Maintenance of industrial electrical equipment. Installation, adjustment, testing, operation and repair of electrical equipment of industrial enterprises Maintenance of industrial electrical equipment
Prospects for the development of the industry
The electric power of all branches of industry, construction and Agriculture increases from year to year. Enterprises receive a large number of new electric motors, ballasts, transformers and high voltage equipment. The construction of new enterprises and workshops requires the construction of cable, air and intrashop networks. But along with this, a large fleet of electrical equipment, devices and networks will be preserved and will be operated.
The branch of science and technology involved in the development and production of electrical machines and transformers is called electrical engineering. Theoretical basis electrical engineering were founded in 1821. M. Faraday, who established the possibility of converting electrical energy into mechanical energy and created the first model of an electric motor. An important role in the development of electrical engineering was played by the work of scientists D. Maxwell and E.Kh. Lenz. Further development the ideas of mutual transformation of electrical and mechanical energies were obtained in the works of outstanding Russian scientists B.S. Jacobi and M.O. Dolivo-Dobrovolsky, who developed and created designs of electric motors suitable for practical use.
Despite the great contribution of Russian scientists to the development of the electric power industry, very little attention was paid to electrification issues in Tsarist Russia. In 1913, electricity generation in Russia was 1.9 billion kWh, and the capacity of all power plants was 1.1 million kW. Therefore, in the first years of Soviet power, the task was set to develop the country's energy base as soon as possible.
In 1920, the VIII All-Russian Congress of Soviets approved the plan for the electrification of Russia (GOELRO), developed at the suggestion of V.I. Lenin. According to the plan, it was envisaged to build 30 power plants with a total capacity of 1.5 million kW within 10-15 years.
The plan for the main indicators was completed in 1931. and already in 1935. the capacity of operating power plants was 4.35 million kW, i.е. the GOELRO plan for electrification was overfulfilled by almost 3 times.
During the first five-year plans, dozens of large power plants were put into operation, including the Zaporizhzhya Dneproges named after. VI Lenin, which at that time was the largest power plant in Europe.
According to the main directions of economic and social society CIS electricity generation in 2000 reached 1880 billion kWh. The construction of nuclear power plants with a total capacity of 6-8 million kW is being carried out with the installation of reactors with a capacity of 1 million kW.
At present, in the Zaporozhye region in the city of Energodar, a nuclear power plant with a capacity of 6 million kW. Work continues to create a unified energy system of the country, for which AC lines of 750 and 1150 thousand volts and direct current lines up to 1200 million volts are being built.
Production efficiency and product quality are largely determined by the reliability of the means of production and, in particular, electrical equipment. A high level of operational reliability of electrical equipment can be ensured by strict adherence to the rules of technical operation during maintenance, a clear organization and modern equipment of repair production, and such a quality of operations for the maintenance, repair and installation of electrical equipment.
The main task of personnel servicing electrical installations is to ensure high reliability and uninterrupted operation. production processes, long-term safety of electrical equipment and economic consumption of electricity.
To a large extent, the implementation of these measures depends on the operating personnel, who, in their practical work, must, at the slightest sign, establish the nature and cause of the malfunction, determine the way to quickly eliminate it, preventing emergency equipment failure.
This is only possible for electricians with good theoretical training, with experience practical work who knows the design and principle of operation of service electrical equipment, the physical processes occurring in machines and apparatuses, the requirements of the rules for the installation of electrical installations (PUE), rules technical operation consumer electrical installations (PTE), safety regulations for the operation of consumer electrical installations (PTB) and instructions for servicing a particular type of equipment and apparatus.
One of the most effective measures to maintain equipment at a high technical level and significantly extend its performance is a modern and high-quality repair. Specialized repair companies often combine the repair of electrical equipment with its reconstruction, improving technical specifications machines and devices, improving their design in order to increase their reliability, power and performance in accordance with the specific requirements of production.
Thus, the reliability of the equipment and, ultimately, the efficiency of the entire production directly depend on the results of the work of each worker involved in the maintenance or repair of electrical equipment. This imposes on the student, who has dedicated his life to the profession of an electrician in the maintenance and repair of electrical equipment, a high responsibility and requires him to have deep solid knowledge and a thorough mastery of working skills and techniques.
Purpose of the machine
Screw-cutting lathe model 1K62 is designed to perform a variety of turning operations, including threading: metric, inch, modular, pitch, Archimedean spiral with a pitch of 3/8 and 7/16. The drive of the spindle 2 of the lead screws 6 and the shaft 7 is carried out through the gearbox located in the headstock 1 and the feed box 8 from the main electric motor M1 hidden inside the bed 9. In addition to the main electric motor, the machine is equipped with an M4 electric motor for high speeds of the established movements of the caliper 3, a cooling pump electric motor M2 and the electric motor of the hydraulic system drive M3, connected using a plug connector ШР. The tailstock 4 of the machine is used to install a second supporting center (when machining in centers) or a cutting tool for machining holes (drill, tap, reamer). The incisors are installed in the head of the caliper, which informs them of the longitudinal and transverse feed.
Rice.
electrical equipment
electrical equipment machine electric motor equipment
On the screw-cutting lathe model 1K62, four three-phase asynchronous electric motors with a squirrel-cage rotor are installed:
a) high-speed electric motor type AO32-4F2 with a power of 1 kW, 1410 rpm, 220\380 V
b) the electric motor of the main drive type A61-4F2 with a power of 10 kW, 1450 rpm, 220\380 V
c) hydraulic motor type AO41-6F2, power 1 kW, 930 rpm, 220\380 V
d) Electric cooling pump type PA-22, power 0.125 kW, 2800 rpm, 220\380 V
Control circuit voltage - 127 V
Local lighting voltage - 36V
The electrical equipment of the machine is placed in a special cabinet.
For the convenience of maintenance and repair during the operation period, the following conditions are met when designing electrical equipment components:
) free access to the connected terminals is provided with a fixing screw. The connecting terminals are located in a closed box with a threaded hole or branch pipe for the input of wires and mechanical fastening of the end elements of the pipeline;
) Ease of replacing or tensioning belts, as well as disengaging clutches;
) Outside the machine, in a conspicuous place near the electric motor, a plate is fixed indicating the direction of its rotation.
The machine provides protection of electrical equipment from short circuit currents by fuses F1-F4 and from overload - by thermal relay KST1-KST2.
Description of the wiring diagram
The machine is energized by turning on the package switch Q1. The control circuit is powered through an isolating transformer T with a secondary voltage of 127V.
The M1 engine is started by the SVP button, by pressing which the KM magnetic starter is turned on. Simultaneously with the switching on of the M2 electric motor (cooling pump electric motor) with the Q2 package switch and M3 (hydraulic system electric motor) turned on with the ShR plug connector turned on.
The M1 electric motor is started by pressing the SBP control button and the idling operation of the electric motor is limited by the time delay of the KT relay. The winding of the time relay KT is switched on by the SQ switch, which closes the contacts when the spindle stops. If the pause in operation exceeds 3-8 minutes, then the relay contact opens and the KM starter is not powered, and the M1 engine stops, thereby limiting the idling operation, reducing power losses.
The operation of the M4 electric motor depends on the movement of the caliper handle, which presses the SAB switch, closes the KMB starter coil circuit through the contact and turns on the engine. Returning the caliper handle to the middle position disables the M4 engine.
Transformer T provides illumination of the machine with a voltage of 36 V. Protection against short-circuit currents is carried out by fuses F1-F5, and against overload - by thermal relays K1, K2, K3. The M4 motor runs for a short time and does not need overload protection.
During installation, the machine must be properly grounded and connected to common system shop grounding. The ground bolt is located at the end of the machine bed in its lower part.
Regularly clean dust and dirt from electric motors and equipment: it is better to use a vacuum cleaner for this purpose.
When caring for magnetic starters, it is necessary to remove dust and dirt from all parts. Worn parts must be replaced in a timely manner.
Choice of current and voltage
In the general case, the choice of voltage and type of current in the power supply system industrial enterprises is made on the basis of technical and economic comparisons of options with different types of current and voltage in terms of non-ferrous metal consumption, in terms of power losses and operating costs.
In this case, there is no such need, since the type of current and the magnitude of the voltage are determined by those adopted for the entire plant.
Since the screw-cutting lathe model 1K62 uses asynchronous AC motors with a standard frequency of 50 Hz and the workshop is supplied with three-phase alternating current with a frequency of 50 Hz, we accept alternating current with a frequency of 50 Hz as the power supply for power electrical equipment.
The presence of an output voltage of an intershop substation of 400\230 Volts corresponds to the voltage of the electrical equipment installed in the shop and does not require a special solution.
Thus, to power the electrical equipment of the machine, we use alternating current with a frequency of 50 Hz, a voltage of 380 V, and for lighting 220V with a frequency of 50 Hz.
Choice of power supply system
The power supply of enterprises is carried out from transformer substations that serve for the conversion and distribution of electricity. They consist of transformer switchgears and control devices.
Workshop transformer substations can be located both inside enterprises and outside them.
To transmit electricity for workshop transformer substations to machine tools (electric motors), electrical networks are used - a set of overhead lines and cable lines of the same voltage. Shop electrical networks consist of insulated wires fixed on insulators or laid in thin-walled steel pipes. The cross section of wires and cables depends on the allowable heating, determined by the magnitude of the electrical load. Excessive heat is dangerous for insulation and contact connections and can lead to fire and explosion.
Reception and distribution of electricity is carried out by power distribution boards, completed from separate panels.
Power is supplied from the step-down substation by a cable laid to the cable well in the channel, and then to the shield along the trench.
A transformer is installed to lower the supply voltage.
A ground loop runs from the outside of the building, and a protective ground network runs inside.
According to the reliability of operation, electrical receivers are divided into 3 categories:
Category I - receivers, the interruption in the power supply of which can lead to a danger to human life or significant material damage associated with equipment damage, mass product defects or a long-term disruption of the technological process.
In terms of reliability of power supply, machines usually belong to category II, however, there are a number of machines when a break in power supply is unacceptable due to possible damage to expensive parts and injury to maintenance personnel. Therefore, such equipment must have at least two independent power sources.
The desire to increase the productivity of modern metalworking equipment causes high demands on frequency and voltage deviations, as well as on the non-sinusoidal coefficient of this voltage.
Repair and maintenance of electrical equipment. Repair of power equipment
The volume and nature of the repair work is determined as a result external examination electric motor, during pre-repair testing and disassembly, as well as after inspection and testing of individual parts.
Before inspection, the machine is cleaned of dirt and dust, blown compressed air outer surface, windings, slip rings, manifold and other accessible parts. During the inspection, they check the completeness (the presence of all the main parts and parts of the machine), the condition of the housing, bearing shields and covers, clamp blocks, output ends and other parts.
As a rule, complete machines are accepted for repair, i.e. those that have all the assembly units and parts. Electric machines of low and medium power are not accepted for repair if their housing or end shield is broken, more than two legs are broken off, the active steel of the cores is damaged to such an extent that at least 25% of new sheets must be added to restore it. Machines with significant damage to mechanical parts that cannot be repaired by the repair shop or enterprise are not accepted for repair. Such machines for their restoration may require significant costs in excess of the cost of a new machine. In addition, after repair, they will not have a sufficiently high operational reliability. In cases where the machine can be repaired without rewinding, pre-repair tests are carried out at idle for 30 minutes before disassembly. Before connecting the electric motor to the network, they check the free running of the rotor, the presence of lubrication in the bearing assemblies, measure the resistance and test the dielectric strength of the insulation. During pre-repair tests at idle, the currents in the phases of three-phase motors are measured, the condition of the mechanical part of the machine, the heating of the bearings, the magnitude of the vibration and a number of other operations are checked. An increase in no-load current in excess of the maximum allowable values may indicate a number of defects: an increase in the air gap, an axial displacement of the rotor relative to the stator, weak pressing of the core, a reduced number of winding turns as a result of an error during the previous repair.
In the process of disassembly, the air gap, the gaps in the bearings are measured.
The unevenness of the air gap should not exceed 10% of the average value.
Electric motor malfunctions occur as a result of wear of parts and aging of materials, as well as in violation of the rules of technical operation.
Malfunctions of electric motors and possible reasons their occurrence.
In accordance with the Rules for Technical Operation, the system of scheduled preventive repairs of electrical equipment provides for two types of repairs: current and overhaul.
Current repairs are carried out at intervals (set by the chief power engineer) for all electric motors in operation. The typical scope of work for current repairs includes the following types of work: external examination motor, flushing and relubrication of bearings and, if necessary, replacement of rolling bearings, checking and repairing fans, cleaning and blowing compressed air windings, checking the state of fastening of the front windings, restoring the varnish coatings of these windings, checking and tightening all threaded fasteners, checking protective grounding , carrying out preventive tests.
Major repairs are carried out in the conditions of an electrical repair shop (ERTS) or a specialized repair company(SRP). The scope of the overhaul includes the work provided for current repairs. It also includes the following types of work: complete disassembly of the electric motor, checking of all components and parts and their fault detection, repair of frames and shield bearings, rotor and stator magnetic circuits, shafts, fans, rotors, elimination of local defects in the insulation of windings and connections, post-repair testing .
Periodicity overhauls electric motors are not established by the Rules for technical operation. They are determined by the person responsible for the electrical facilities of the enterprise based on estimates common work electric motors (duration) and local conditions operations.
Repair of control equipment
The current repair of control devices consists of the following operations:
1. Partial disassembly, cleaning and washing of parts, hinges and axles.
Careful inspection of parts and assemblies in order to detect defects and malfunctions.
Replacement of defective parts and assemblies, elimination of violations of the correctness of their interaction.
Elimination of defects in contact surfaces (films, oxides, traces of erosion, soot, etc.) checking and adjusting the simultaneity of switching on, contact density, contact pressure.
Integrity checks and cleaning from metal spatter of arc chutes.
Control of the absence of mechanical damage and restoration of damaged insulation
Verification of tightness of armature and core.
Repair of mechanical components, lubrication of bearings and swivel joints.
Checks and adjustments of control and protection relays.
Overhaul is carried out with a complete disassembly of electrical appliances in specialized units with a high level of mechanization of production. The devices are dismantled and replaced with new ones.
When repairing magnetic starters with a thermal relay, attention is paid to the condition of these relays, the integrity of the heating elements. When replacing, use only factory-made relay elements
The adjustment of the dips, as well as the simultaneity of touching the contacts of different poles, is carried out using shims, which are laid between the contact holder and the traverse.
Adjustment of the contact pressure is carried out by measuring the compression of the contact springs. In many devices, this is done by changing the length of the springs using adjusting screws or nuts.
When repairing magnetic starters, the initial and final compression of the contact system is checked. The initial pressure is the force exerted by the contact spring at the point of initial contact. With insufficient initial pressure, welding of the contacts may occur, and with an increased pressure, the accuracy of the operation of the device will be disturbed. Pressing should be in the range of 50-60 kN. End push is the force exerted by the contact spring at the point of end contact when the starter is fully engaged. This value should be in the range of 90-110 kN. The initial and final contact compression of the devices is measured with a dynamometer. With the help of a loop and a dynamometer, the contact is pulled away from the contact holder. The beginning of the deformation of the spring is judged by the movement of a strip of thin paper previously placed between the contact holder and the contact. The tightness of the armature to the core is also adjusted. Irregularities in the joint of the ends of the magnetic circuit in the air gap leads to an increase in current, heating, noise and vibration. Therefore, only such irregularities in the joint are allowed, in which the total density of the anchor to the core is less than 70% of the area cross section joint.
The interaction of all parts adjusted during the repair period is checked by turning on the magnetic starter several times by hand. Checking and testing of the magnetic starter is carried out according to the manufacturer's program. The results of post-repair test readings should not differ by more than 10% from factory test data.
Maintenance of power equipment
Before starting up the newly installed equipment and the electric motor or after installing the installation (unit), the place where the electric motor is installed is cleaned of debris, dust, dirt, then carefully inspect the internal parts, check for foreign objects in the machine, blow the electric motor with dry compressed air at a pressure not higher than 0.2 MPa.
They measure the insulation resistance, check the condition of the external bolted connections, and, if necessary, tighten them, inspect the supply cables and the tightening of the grounding bolts, check the compliance of the mains voltage with the voltage indicated on the electric motor shield, turn the rotor manually, measure the correct mating of the motor shafts and the drive mechanism.
Inspections of electric motors in operation, their control and protection systems are carried out according to the schedule approved by the chief power engineer of the enterprise. Inspection and testing of grounding is carried out daily (if there is a person on duty).
When inspecting electric motors, the temperature of bearings, windings, housings, load, and vibration are monitored. They check the cleanliness of the machine, the room, the cooling medium, the operation of the bearings, the serviceability of the guards.
Bearing temperature is measured using a thermometer. For rolling bearings, the temperature is measured on the outer ring when the machine is stopped. The maximum allowable temperature must not exceed .
When inspecting electric motors, they check with an ohmmeter whether there is a break in the grounding conductor of the cable.
The condition of the coupling or pulley is checked, paying special attention to the details of the coupling. Damaged rubber parts are replaced. A 500V megohmmeter measures the insulation resistance of the stator windings of electric motors relative to the housing. The insulation resistance must be at least 0.5 Mohm at a temperature 
.
Carefully inspect the board of clamps. In the presence of chips, cracks and charring of the surface, the board is replaced. Traces of overlapping with an arc are cleaned with a sandpaper, degreased with white alcohol or acetone and covered with bakelite varnish or BF-2 glue.
Bearings after 4000 hours of work, but at least once a year, are washed with kerosene, and then filled with grease for 2/3 of the volume of the bearing seat. Grease grades must be suitable for the operating conditions of the bearings.
To ensure the normal operation of the electric motor, it is necessary to maintain the voltage on the buses of the supply substation in the range from 100 to 105% of the nominal. For production reasons, the operation of the electric motor is allowed with voltage deviations from -5 to + 10% of the nominal.
When the temperature of the stator winding should not exceed by , and the rotor winding by the temperature of the cooling air.
During maintenance, the motor insulation resistance is periodically checked. For stator windings, the insulation resistance must be at least 10 MΩ, for rotor windings - 1.5 MΩ. If the insulation levels are not as specified, the windings are dried.
Maintenance of control equipment
Maintenance of electric devices up to 1000V consists of periodic inspections, inspections, cleaning and minor repairs. The frequency of maintenance is set by local regulations depending on the operating conditions, but not earlier than 1 time in 2-3 months.
During maintenance of electric devices with voltage up to 1000V, the following types of work are carried out: cleaning, external and internal inspection, elimination of defects found and tightening of fastening threads; heating control of contacts, coils and other conductive elements; cleaning contacts from contamination, oxides, melting and adjustment from simultaneous closing and opening; replacement of fuses and faulty fuses; checking the electrical wiring.
Before starting the inspection, the voltage is turned off and measures are taken to exclude the possibility of its appearance on the main contacts and auxiliary contacts.
Inspections of magnetic starters are carried out with particular care, since the operation of technological equipment depends on their reliable operation.
The magnetic starter is switched on manually, they are convinced of the free movement of the movable system, the presence of contact between the movable and fixed contacts, the absence of distortions of the contact circuit, the serviceability of the contact springs. Springs that have lost their elastic properties or are damaged are replaced. When inspecting the arc chutes of magnetic starters, they remove soot with a cleaning cloth soaked in white spirit or gasoline. Splashes of metal on the gratings are cleaned off with a file.
The thickness of the ceramic-metal layer of contacts is measured. If the thickness of the ceramic-metal layer is less than 0.5 mm, the contacts are replaced.
Inspect the coil of the magnetic starter, make sure that there is no damage to the outer coating of the winding, as well as leaks of the top coat as a result of overheating. Check the tightness of the coil on the core.
Check the condition of the magnetic system and the short-circuited coil. The contact surfaces of the magnetic circuit are cleaned with a cleaning material. Corrosion on other surfaces of the magnetic starter is removed with sandpaper and covered with air-drying varnish. Check the heating element. In case of warping, metal burnout or coil shorting, the element must be replaced. The bimetallic plate is replaced in case of deformation and burning. After replacing the heating element or bimetallic plate, the relay is connected to a device or circuit that allows you to smoothly adjust the value of the test current. Next, inspect the insulating parts of the magnetic starters to make sure that there are no chips or cracks.
Fuses require constant monitoring, replacement of blown fuses and timely repair. Reliable and safe operation of electrical installations depends on their serviceability, correct selection of the insert. To speed up the selection and replacement of a blown insert, each fuse must have a clear figure for the rated current.
Occupational Safety and Health. Organization of the workplace of an electrician
Proper organization of the workplace ensures rational movements of the worker and reduces to a minimum the time spent on finding and using tools and materials.
The mobile table is used when disassembling, washing and assembling various electrical equipment. He also serves vehicle for cargo transportation. The tabletop is lined with paper - laminated plastic with a steel corner edging. At the bottom of the table there is a metal shelf made of steel sheet 1.5 mm thick, designed for storing technological equipment and auxiliary materials.
The table is mounted on a wheel (with a low-resistance rubber rim) with rolling bearings. This provides good maneuverability and does not require much effort to move it.
The framework of a case - a rack is painted with gray enamel.
The mobile table is used for disassembling, washing and assembling various electrical equipment, and also serves as a vehicle for transporting goods. The table is mounted on wheels with bearings. This provides good maneuverability and does not require much effort to move it.
The duty electrician's portable bag is used for carrying tools and measuring equipment, fixtures, small parts for repairing electrical equipment in the workshop area.
The design of a chair - a stool provides the most working convenient pose. The seat can be easily and quickly raised or lowered.
The workplace must have technical and accounting documentation, job description, as well as documentation on the organization and safety of work.
The technical documentation includes: electrical diagrams of the most complex machines, hoisting and transport equipment, basic circuit diagram power supply of the workshop (section), electric circuit of switchboards, etc.
Accounting documentation reflects the project of equipment and the work of an electrician. One of the types of such documentation is an operational (operational) log.
As a mandatory document at the workplace of an electrician, there should be an instruction on labor safety for a shop electrician servicing electrical installations up to and above 1000V.
Documentation on the organization of labor includes: a calendar schedule of preventive examinations, a shift-hour schedule and a map of the organization of work of the electrician on duty.
The workplace of an electrician must be designed in accordance with the requirements of technical aesthetics. The work clothes of an electrician should be comfortable, not restrict movement during work, and consist of a jacket, trousers and a beret (beret in a bright color - red, orange or brown).
Organizational and technical measures to ensure the safety of work in electrical installations
The technical measures that ensure the safety of work in electrical installations include:
a) shutdown of the installation with the implementation of measures that exclude the erroneous supply of voltage to the place of work;
b) installation of fences and hanging posters;
c) checking the absence of voltage;
d) overlay grounding.
Disconnection can be performed using: manually operated switching devices, the position of the contacts of which is visible from the front side or determined by examining the panels from the rear side, opening the shields. Contactors or other remote devices after taking measures to eliminate the possibility of erroneous switching on (removing the auxiliary current fuses, disconnecting the ends of the closing coil).
On the drives of disconnectors, separators and control keys, as well as on the bases of the fuses, with the help of which voltage can be supplied to the place of work, posters are posted: “Do not turn on! People are working." Posters or warning signs should be posted on temporary fences: “Stop! Voltage".
Checking the absence of voltage between all phases and each phase in relation to the ground and the neutral wire on the part of the electrical installation that is disconnected for work is carried out by the permitter after warning posters are posted.
To protect the worker from possible electric shock, in case of erroneous voltage supply to the current-carrying parts of all phases of the disconnected. For the operation of the electrical installation, grounding is applied from all sides, from where voltage can be supplied, including as a result of reverse transformation.
Organizational activities include:
a) Issuing an order or order;
b) Permission to work;
c) supervision during work;
d) registration of breaks in work, transitions to another workplace;
e) registration of the completion of work.
Responsible for the safety of work are the persons issuing the order: the responsible head of the robot is the person of the operational personnel who allows them to work; work producer; watching; workers in the team.
The right to issue orders for the production of work in electrical installations is granted to persons of the electrical personnel of the enterprise (head of the electrical department, head of the operation service, foreman), authorized to issue orders by order of the chief power engineer. These persons must have a qualification group V (in installations with a voltage of 1 kV - not lower than IV).
The complete completion of the work, indicating the date and time, is drawn up at the end of the order with the signature of the work foreman.
Allowing to work together with the responsible manager and the foreman (or supervisor) check the correctness of the preparation of the workplace and the composition of the team.
Supervision during work is carried out by the foreman (or supervisor), who should not be disconnected from the team.
Upon completion of all the work recorded in the order, the workplace must be inspected by the responsible manager, who, after the departure of the brigade, signs the order and hands it over to the operational staff.
Protective earth
Grounding is the intentional connection of any part of an electrical installation to ground. Protective grounding is called, performed for the electrical safety of people and farm animals.
The principle of grounding protection is to reduce the voltage on the case when a current is shorted to it. When grounding is not available, the shorted case has a phase voltage with respect to ground. Touching it is just as dangerous as touching a live part. Grounding causes voltage redistribution. The case connected to ground electrode 2 will take its voltage equal to: U3=I3R3, where I3 is the fault current on this resistance, and will be many times less than in the absence of grounding.
Fault currents to the case are diverted to the ground through the ground electrode, i.e. a conductor or group of conductors in direct contact with earth. In electrical installations with voltage up to 1000V with an isolated neutral, grounding devices must have a resistance of not more than R ≤ 4 Om
With a total power of power supplies of 100 kVA and less, they allow resistance R ≤ 10 Om
Protective zeroing
Protective grounding, as a rule, is used in three-phase four-wire networks with a solidly grounded neutral with a voltage of up to 1000 V.
In these networks, grounding does not provide reliable protection.
To protect people from this voltage, it is necessary to reliably and quickly automatically disconnect the damaged section of the network. For this purpose, zeroing is arranged.
Grounding is the intentional connection of parts of an electrical installation to the grounded neutral of a transformer or generator. In the presence of grounding, the short-circuit current does not flow through the ground, but through the grounding metal conductors and, therefore, has a large value sufficient to burn out the fusible links or trip the protection. The short-circuit current acts on automata or fuse-links, which turn off the damaged section of the network and thereby eliminate dangerous potentials on the cases.
The fault current to the case does not flow through the ground, as was the case in the absence of grounding, but through the circuit: phase wire - neutral wire.
Zero is a wire connected to the grounded neutral of a transformer or generator.
The reliability of protective grounding depends on the resistance Rf and Rh of the circuit; phase wire - neutral wire.
For reliable and fast disconnection, it is necessary that the short-circuit current Ish exceeds the rated current of the fuse link
Ikz ≥ K Inom,
Where Inom is the rated current of the fuse-link;
K is the coefficient of reliability.
List of used literature
V.B. Atabekov Repair of electrical equipment of industrial enterprises 1989 V.Sh. Moscow
A.S. Kokarev Electrician for the repair of electrical machines 1979 V.Sh. Moscow
Yu.V. Kornilov Maintenance of electrical installations of industrial enterprises 1986 V.Sh. Moscow
Yu.D. Sibikin Maintenance of electrical installations of industrial enterprises 1989 V.Sh. Moscow
Yu.D. Sibikin Handbook of a young worker on the operation of industrial enterprises, 1992 V.Sh. Moscow
G.P. Vartanov Electrician - repairman 1977 V.Sh. Moscow
A.A. Voronina Safety measures when working in electrical installations 1974 V.Sh. Moscow
A.M. Gurzhiy Electrical engineering with the basics of industrial electronics Kyiv "Forum" 2002
Organization of operation and repair of electrical equipment at INDUSTRIAL ENTERPRISES
Tutorial
"Installation, adjustment, operation and repair of the power supply system of industrial enterprises"
for students studying in the specialty "Electrical equipment and electrical facilities of enterprises, organizations and institutions"
Moscow MPEI Publishing House 2011
UDC
Approved educational administration MPEI (TU)
as a teaching aid for students
Prepared at the Department of Power Supply of Industrial Enterprises
Reviewers: Cand. tech. Sciences, Associate Professor E.V. Borisova
(State Educational Institution of Higher Professional Education "MATI" - Russian State Technical University named after K.E. Tsiolkovsky),
Professor G.F. Bystritsky
(Moscow Energy Institute)
THEM. Khevsuriani, A.V. Kondratiev, A.V. Ragutkin
K-642 Organization of operation and repair of electrical equipment at industrial enterprises: study guide / I.M. Khevsuriani, A.V. Kondratiev, A.V. Ragutkin. - M.: MPEI Publishing House, 2011. - 64 p.
The main questions of the organization of operation and repair of the power supply system of industrial enterprises are considered. The main provisions of the organization of the operation of the electrical economy, the procedure for commissioning electrical installations are presented. Documents accompanying the repair work are given. The issues of operation and repair of overhead and cable power lines are considered.
For students of specialty 140610 "Electrical equipment and electrical facilities of enterprises, organizations and institutions".
ISBN Moscow Power Engineering Institute
(technical university), 2011
foreword
The course "Installation, adjustment, operation and repair of the power supply system of industrial enterprises" is one of the major disciplines for students studying in the specialty "Electrical equipment and electrical facilities of enterprises, organizations and institutions."
The course contains four independent chapters that characterize life cycle power supply systems of industrial enterprises: installation, adjustment, operation, repair.
This manual considers most of the main issues on the organization of operation and repair of the power supply system, as well as the issues of operation and repair of overhead power lines and cable lines.
As a rule, the supply lines of the power system have a voltage of 35-110-220 kV and more, and distribution networks 6-10-35 kV.
The main task of personnel servicing electrical installations is to ensure reliable and uninterrupted power supply to consumers, long-term safety of electrical equipment and economical use of electricity.
A high level of operational reliability of electrical equipment can be achieved by strict adherence to the rules of technical operation during maintenance, a clear organization of preventive tests and measurements while observing safe working conditions.
One of the most effective measures to maintain electrical equipment at a high technical level and significantly extend its performance is timely and high-quality repairs. Specialized repair production units or enterprises often combine the repair of electrical equipment with its reconstruction, improving the technical parameters of machines and devices, improving their design and performance in accordance with production requirements.
Publication planned for the future teaching aids, including materials for the operation and repair of transformer substations, electrical machines and other equipment of the power supply system.
Maintenance and repair of industrial equipment is a set of actions necessary to maintain or restore the performance of electrical devices of an enterprise. For the efficient operation of electrical installations, it is important to competently organize their maintenance, timely preventive and repair work, compliance with safety rules and the requirements of regulatory documentation.
Maintenance and repair of electrical equipment of industrial enterprises provide:
. preservation of the primary operational qualities of electrical devices;
. maintaining the constant operability of production equipment with specified operating parameters throughout the entire period of operation;
. time regulation forced downtime, overhaul intervals, repair cycles;
. reducing the risk of premature wear, breakdown of devices, accidents at work;
. increasing the efficiency of mechanisms, extending their service life while maintaining efficiency and safety of use;
. identification and elimination of emerging problems and their causes;
. timely preparation of the necessary spare parts and Supplies;
. reducing the cost of restoration and forced replacement of faulty mechanisms;
. increase in labor productivity;
. reducing the cost of production;
. increase in the company's profits.
From the first days of the victory of the October Socialist Revolution and the transition to the peaceful construction of socialism in our country, the people faced the task of restoring industry destroyed by the civil war and intervention.
The equipment we inherited from Tsarist Russia was so worn out or damaged that it could only be used after a major or refurbishment.
Soviet Russia was in the ring of hostile capitalist states, so there was nowhere to wait for help and nowhere to get the necessary machine tools, mechanisms and machines.
There was only one way out: restore the industry on their own. And then, at the call of V. I. Lenin, the workers of factories and factories, as the true owners of the country, began to restore enterprises, repair existing equipment.
In a relatively short period of time, using the repaired equipment of factories, factories and mines, our people managed not only to restore the pre-revolutionary level of industrial production, but also to significantly surpass it, and then proceed to the electrification and industrialization of the country.
Lenin's plan for the creation material basis socialism in our country on the basis of its electrification- the first state long-term plan for restoration and socialist reconstruction National economy Soviet Russia on the highest technical basis.
It specified the main tasks in the field of energy very clearly: creation of powerful district thermal power plants using local fuels; extensive construction of hydroelectric stations and high-voltage transmission lines; organization of regional energy systems with the prospect of their integration into a single high-voltage network of the country. The plan provided for the restoration, reconstruction, expansion of the pre-war electrical facilities and the construction of 30 new power plants.
The Soviet people enthusiastically undertook the implementation of the great plan. It is no coincidence that the VIII Congress of Soviets, which approved the GOELRO plan, expressed its unshakable confidence that all Soviet institutions, all Soviets of Deputies, all workers and working peasants will exert all their strength and stop at no sacrifice to implement the plan for the electrification of Russia at all costs and in spite of all obstacles.
Following the Leninist course, the people, under the leadership of the Party and the government, succeeded in transforming our country into a powerful industrial power, creating the material and technical base of communist society on the basis of electrification.
New frontiers for the development of the electric power industry in our country were established by the 24th Congress of the CPSU. The continuous advance development of the electric power industry in the Soviet Union, as well as the annually increasing production and introduction of various electrical equipment in all branches of the national economy, put forward the demand for organizing the repair of electrical machines and apparatus on such a scale and at such a technical level that would ensure their long-term normal operation.
Speaking at the 24th Congress of the CPSU and pointing out the need to make maximum use of the equipment available in the country, Comrade L. I. Brezhnev said: “There is now a huge amount of various equipment in the country, and if we use it clumsily or incompletely, unjustifiably shorten its life, then this causes significant damage to the people's interests.”
One of the most effective means of maintaining equipment in good condition technical condition and extending the life of equipment is, as you know, its timely and high-quality repair.
The volume and complexity of electrical equipment being repaired is increasing every year, and therefore there is a need for continuous improvement of technology and reduction of repair time, increasing the technical equipment of repair shops and enterprises, attracting the most qualified repair workers to repair work, and developing rationalization activities of repair personnel.
Recently, the equipment of repair enterprises has improved, the activities of innovators have expanded more widely, which has made it possible not only to qualitatively change the nature of the work of repair personnel, but also to significantly improve repair technology and, on this basis, reduce its cost.
So, thanks to the improvement of technology and, in particular, the transition to the flow-nodal method, the cost of repairing electric motors with a capacity of up to 100 kW decreased in 1970 compared to 1965 by an average of 15%, and electrical apparatus voltage up to 1000 V - by 26%. Reducing the cost of repairing electrical equipment is of great economic importance, since a 1% reduction in government spending for these purposes allows saving tens of millions of rubles annually.
The main role in improving all the economic and technical indicators of the repair belongs to the repair workers. Ultimately, all indicators of repair depend on their knowledge of the designs of machines, apparatus and instruments, their ability to identify malfunctions and establish their causes, as well as their knowledge of the most advanced methods of repairing equipment.
A modern worker engaged in the repair of electrical equipment must be a comprehensively trained specialist. This book is designed to serve the task of training qualified repair personnel. To deepen the knowledge of repair certain types industrial electrical equipment electricians-repairmen are advised to refer to the special literature, a list of which is given at the end of the book.
The textbook is written based on the experience of electrical workshops machine-building plants. It takes into account the advanced repair methods used in specialized electrical repair plants. The book describes the organization and technology of repair of electrical machines and apparatuses for general use.
Repair of technological electrical equipment of enterprises, as well as electrical apparatus of special design (tropical version, for the Far North, etc.) is not considered in the textbook.
The third edition of the book is supplemented with lists of basic requirements for the repair of explosion-proof electrical equipment and mandatory operations for the repair of relay protection and automation devices, a description of methods for checking the axial and radial clearances of rolling bearings.
The presentation of the material in the book corresponds to the training program for electricians for the repair of electrical equipment of industrial enterprises, approved by State Committee Council of Ministers of the USSR for vocational education.
"Repair of electrical equipment of industrial enterprises",
V.B. Atabekov
Name Quantity Technical data or characteristics Cable knives (a, b) 2 Special for sheath cutting - with a retractable blade or cutting disc Pliers PK-1 with a set of punches and dies 1 For crimping cable lugs on current-carrying conductors with a cross section of 16 - 50 mm2 1 with crimping tool for cable lugs 1 Same, for conductors…
The MP-1 mass is heated to 120 - 130 ° C and the divided section of the cable is thoroughly scalded. Then, starting from a point located 50 mm from the installation site of the porcelain bushings, the cable cores are wound with three or four layers of adhesive PVC tape in the direction from the base of the groove to the ends of the cores to their bare sections. The tape is applied with semi-overlapping turns. (If there is no sticky...
If damage occurs inside the cast-iron coupling, it is dismantled. For dismantling, the coupling is raised by 150 - 200 mm above the bottom of the trench, placing bricks or boards under the cables on both sides of the coupling; remove the bolts securing the upper and lower halves of the coupling; heat both halves of the coupling with a blowtorch flame and separate them from each other by turning a screwdriver, a blade ...
In the previously marked places for the installation of bushings on the cores, a conical winding is made from tapes used to seal the cores, and on the cable armor at the location of the funnel neck, a conical winding from a resin tape is performed. At the same time, the ground wire soldered to the armor and cable sheath is laid at half the thickness of the winding with a resin tape (after about 3-4 layers) ....
To connect or terminate cables, it is necessary to cut their ends. Cutting is the operation of stepwise removal of protective and insulating parts from the cable. The dimensions of the cut are determined by the design of the coupling or funnel, the voltage of the cable, the conditions for connecting the cable and the cross section of its cores. Finished cutting of the end of a three-core cable Finished cutting of the end of a three-core cable with paper insulation: 1 - outer jute cover, ...
Epoxy cable terminations are characterized by ease of execution, reliable tightness, as well as high electrical and mechanical strength, which allows them to be made without the use of porcelain bushings and a protective metal casing. At the same time, they are fireproof and heat-resistant: the operating temperatures of these terminations are from -50 to + 90 °C. They have a common type designation KVE and are used for ...
The current-carrying conductors of the cables are connected by soldering, crimping or welding. Soldering and crimping of the cores are carried out in sleeves, and welding is carried out in a thermite cartridge. The connection of current-carrying conductors of cables by soldering in sleeves is carried out by the method of irrigation. POS-30 or ShS-40 solder melted in the ladle is poured into the filling holes of the sleeves, into which the cable cores are placed. The connection of cable cores by soldering is performed, observing the following ...
When installing the KVEN epoxy termination, the cores are wound with a sticky polyvinyl chloride tape in a run-up to prevent their insulation from being deployed when putting on them tubes of nayrite rubber. Degrease with acetone or gasoline the inner and outer surfaces of the end of the tube, which should be filled in the epoxy housing, and after 5 - 6 minutes (after volatilization ...
The connection of current-carrying conductors of cables by crimping in sleeves is performed in the following sequence. The inner surface of the sleeve 1 is cleaned to a metallic sheen with a steel ruff 2, and the ends of the wires to be connected 4 with a brush 3 made of cardolent. Give a round shape to the multi-wire sector cores of the connected cables with universal pliers. The cores are inserted into the sleeve so that their ends fit snugly against each other ...
End fittings KVED, KVEp and KVEZ are mounted basically in the same way as the KVEN termination, but their installation has some features, the description of which is given below. The KVED epoxy seal is used in damp areas, so the nayrite rubber tube used in the KVEN seal is replaced by a two-layer tube 12. The lower layer of the PVC tube is able to withstand the damaging effects of oils ...
Welding of current-carrying conductors of cables in a thermite cartridge is carried out in the following sequence. They clean and then degrease the ends of the connected wires with acetone or gasoline. Install a thermite cartridge on the cores. Seal the cores with asbestos cord. Strengthen the thermite cartridge and the wires to be connected in the thermite welding fixture. Cooling tongs are fixed on the cores to remove heat. Ignite a thermite cartridge with a special match. Introducing…
After repair, cables with voltage up to 1 kV are tested with a megger for 1000 b. At the same time, the condition of the cable insulation is checked, whether there is a break in the cable cores, phase grounding or asymmetry in the insulation resistance of individual phases. Cables supplying critical consumers are recommended to be tested with rectified direct current from special kenotron installations. In this case, tests with a megohmmeter should be carried out before and after ...
prospects development industries
The electric power of all branches of industry, construction and agriculture is increasing from year to year. Enterprises receive a large number of new electric motors, ballasts, transformers and high-voltage equipment. The construction of new enterprises and workshops requires the construction of cable, air and intrashop networks. But along with this, a large fleet of electrical equipment, devices and networks will be preserved and will be operated.
The branch of science and technology involved in the development and production of electrical machines and transformers is called electrical engineering. The theoretical foundations of electrical engineering were laid in 1821 by M. Faraday, who established the possibility of converting electrical energy into mechanical and created the first model of the electric motor. An important role in the development of electrical engineering was played by the work of the scientists D. Maxwell and E. Kh. Lenz. The idea of mutual conversion of electrical and mechanical energies was further developed in the works of outstanding Russian scientists B.S. Yakobi and M.O. Dolivo-Dobrovolsky, who developed and created designs of electric motors suitable for practical use.
Despite the great contribution of Russian scientists to the development of the electric power industry, very little attention was paid to electrification issues in Tsarist Russia. In 1913, electricity generation in Russia was 1.9 billion kWh, and the capacity of all power plants was 1.1 million kWh. Therefore, in the first years of Soviet power, the task was set to develop the country's energy base as soon as possible.
In 1920, the VIII All-Russian Congress of Soviets approved the plan for the electrification of Russia (GOELRO), developed at the suggestion of V. I. Lenin. The plan provided for the construction of 30 power plants with a total capacity of 1.5 million kW within 10-15 years.
The plan for the main indicators was completed in 1931, and already in 1935 the capacity of existing power plants was 4.35 million kW, i.e., the GOELRO plan for electrification was exceeded by almost 3 times.
During the first five-year plans, dozens of large power plants were put into operation, including the Zaporizhzhya Dneproges named after. VI Lenin, which at that time was the largest power plant in Europe.
According to the main directions of the economic and social society of the CIS, electricity generation in 2000 reached 1880 billion kWh. The construction of nuclear power plants with a total capacity of 6-8 million kW with the installation of reactors with a capacity of 1 million kW is underway.
At present, a nuclear power plant with a capacity of 6 million kW has been put into operation in the city of Energodar in the Zaporozhye region. Work continues to create a unified energy system of the country, for which AC lines of 750 and 1150 thousand volts and direct current lines up to 1200 million volts are being built.
Production efficiency and product quality are largely determined by the reliability of the means of production and, in particular, electrical equipment. A high level of operational reliability of electrical equipment can be ensured by strict adherence to the rules of technical operation during maintenance, a clear organization and modern equipment of repair production, and such a quality of operations for the maintenance, repair and installation of electrical equipment.
The main task of personnel servicing electrical installations is to ensure high reliability and uninterrupted operation of production processes, long-term safety of electrical equipment and economic consumption of electricity.
To a large extent, the implementation of these measures depends on the operating personnel, who, in their practical work, must, at the slightest sign, establish the nature and cause of the malfunction, determine the way to quickly eliminate it, preventing emergency equipment failure.
This can only be done by electricians with good theoretical training, who have practical work experience, who know the design and principle of operation of service electrical equipment, the physical processes occurring in machines and apparatuses, the requirements of the rules for the installation of electrical installations (PUE), the rules for the technical operation of consumer electrical installations (PTE), rules safety precautions for the operation of consumer electrical installations (PTB) and maintenance instructions specific type equipment and devices.
One of the most effective measures to maintain equipment at a high technical level and significantly extend its performance is a modern and high-quality repair. Specialized repair companies often combine the repair of electrical equipment with its reconstruction, improving the technical parameters of machines and devices, improving their design in order to increase their reliability, power and performance in accordance with specific production requirements.
Thus, the reliability of the equipment and, ultimately, the efficiency of the entire production directly depend on the results of the work of each worker involved in the maintenance or repair of electrical equipment. This imposes on the student, who has dedicated his life to the profession of an electrician in the maintenance and repair of electrical equipment, a high responsibility and requires him to have deep solid knowledge and a thorough mastery of working skills and techniques.
Purpose machine tool
The screw-cutting lathe model 1K62 is designed to perform a variety of turning operations, including threading: metric, inch, modular, pitch, Archimedean spiral with a pitch of 38 and 716. The drive of the spindle 2 lead screws 6 and shaft 7 is carried out through a gearbox, located in the headstock 1 and the feed box 8 from the main electric motor M1, hidden inside the frame 9. In addition to the main electric motor, the machine is equipped with an M4 electric motor for high-speed movements of the caliper 3, the M2 cooling pump electric motor and the M3 hydraulic system drive electric motor, connected using a ShR plug connector. The tailstock 4 of the machine is used to install a second supporting center (when machining in centers) or a cutting tool for machining holes (drill, tap, reamer). The incisors are installed in the head of the caliper, which informs them of the longitudinal and transverse feed.
2.2 electrical equipment
On the screw-cutting lathe model 1K62, four three-phase asynchronous electric motors with a squirrel-cage rotor are installed:
a) AO32-4F2 type high-speed electric motor with a power of 1 kW, 1410 rpm, 220 380 V b) A61-4F2 type main drive electric motor with a power of 10 kW, 1450 rpm, 220 380 V c) AO41-6F2 type hydraulic hydraulic motor with a power of 1 kW, 930 rpm, 220 380 V d) Electric cooling pump type PA-22 with a power of 0.125 kW, 2800 rpm, 220 380 V Control circuit voltage - 127 V Local lighting voltage - 36 V The electrical equipment of the machine is located in a special cabinet.
For the convenience of maintenance and repair during the operation period, the following conditions are met when designing electrical equipment components:
1) free access to the connected terminals is provided with a fixing screw. The connecting terminals are located in a closed box with a threaded hole or branch pipe for the input of wires and mechanical fastening of the end elements of the pipeline;
2) Ease of replacing or tensioning belts, as well as disengaging clutches;
3) Outside the machine, in a conspicuous place near the electric motor, a plate is fixed indicating the direction of its rotation.
The machine provides protection of electrical equipment from short circuit currents by fuses F1-F4 and from overload by thermal relay KST1-KST2.
Description wiring diagrams
The machine is energized by turning on the package switch Q1. The control circuit is powered through an isolating transformer T with a secondary voltage of 127 V.
The M1 engine is started by the SVP button, by pressing which the KM magnetic starter is turned on. Simultaneously with the switching on of the M2 electric motor (cooling pump electric motor) with the Q2 package switch and M3 (hydraulic system electric motor) turned on with the ShR plug connector turned on.
The M1 electric motor is started by pressing the SBP control button and the idling operation of the electric motor is limited by the time delay of the KT relay. The winding of the time relay KT is switched on by the SQ switch, which closes the contacts when the spindle stops. If the pause in operation exceeds 3-8 minutes, then the relay contact opens and the KM starter is not powered, and the M1 engine stops, thereby limiting the idling operation, reducing power losses.
The operation of the M4 electric motor depends on the movement of the caliper handle, which presses the SAB switch, closes the KMB starter coil circuit through the contact and turns on the engine. Returning the caliper handle to the middle position disables the M4 engine.
Transformer T provides illumination of the machine with a voltage of 36 V. Protection against short-circuit currents is carried out by fuses F1-F5, and against overload - by thermal relays K1, K2, K3. The M4 motor runs for a short time and does not need overload protection.
During installation, the machine must be reliably grounded and connected to the general grounding system of the workshop. The ground bolt is located at the end of the machine bed in its lower part.
Regularly clean dust and dirt from electric motors and equipment: it is better to use a vacuum cleaner for this purpose.
When caring for magnetic starters, it is necessary to remove dust and dirt from all parts. Worn parts must be replaced in a timely manner.
Choice current And voltage
In the general case, the choice of voltage and type of current in the power supply system of industrial enterprises is made on the basis of technical and economic comparisons of options with different types current and voltage in terms of non-ferrous metal consumption, in terms of power losses and operating costs.
In this case, there is no such need, since the type of current and the magnitude of the voltage are determined by those adopted for the entire plant.
Since the screw-cutting lathe model 1K62 uses asynchronous AC motors with a standard frequency of 50 Hz and the workshop is supplied with three-phase alternating current with a frequency of 50 Hz, we accept alternating current with a frequency of 50 Hz as the power supply for power electrical equipment.
The presence of an output voltage of an intershop substation of 400 230 Volts corresponds to the voltage of the electrical equipment installed in the shop and does not require a special solution.
Thus, to power the electrical equipment of the machine, we use alternating current with a frequency of 50 Hz, a voltage of 380 V, and for lighting 220 V with a frequency of 50 Hz.
Choice systems electricity supply
The power supply of enterprises is carried out from transformer substations that serve for the conversion and distribution of electricity. They consist of transformer switchgears and control devices.
Workshop transformer substations can be located both inside enterprises and outside them.
To transmit electricity for workshop transformer substations to machine tools (electric motors), electrical networks are used - a combination of overhead lines and cable lines of the same voltage. Shop electrical networks consist of insulated wires fixed on insulators or laid in thin-walled steel pipes. The cross section of wires and cables depends on the allowable heating, determined by the magnitude of the electrical load. Excessive heat is dangerous for insulation and contact connections and can lead to fire and explosion.
Reception and distribution of electricity is carried out by power distribution boards, completed from separate panels.
Power is supplied from the step-down substation by a cable laid to the cable well in the channel, and then to the shield along the trench.
A transformer is installed to lower the supply voltage.
A ground loop runs from the outside of the building, and a protective ground network runs inside.
According to the reliability of operation, electrical receivers are divided into 3 categories:
Category I - receivers, the interruption in the power supply of which can lead to a danger to human life or significant material damage associated with equipment damage, mass product defects or a long-term disruption of the technological process.
In terms of reliability of power supply, machines usually belong to category II, however, there are a number of machines when a break in power supply is unacceptable due to possible damage to expensive parts and injury to maintenance personnel. Therefore, such equipment must have at least two independent power sources.
The desire to increase the productivity of modern metalworking equipment causes high demands on frequency and voltage deviations, as well as on the non-sinusoidal coefficient of this voltage.
Repair And service electrical equipment. Repair power equipment
The volume and nature of repair work is determined as a result of an external examination of the electric motor, in the process of pre-repair testing and disassembly, as well as after inspection and testing of individual parts.
Before inspection, the machine is cleaned of dirt and dust, the outer surface, windings, slip rings, manifold and other accessible parts are blown with compressed air. During the inspection, they check the completeness (the presence of all the main parts and parts of the machine), the condition of the housing, end shields and covers, clamp blocks, output ends and other parts.
As a rule, complete machines are accepted for repair, i.e. those that have all Assembly units and details. Electric machines of low and medium power are not accepted for repair if their housing or end shield is broken, more than two legs are broken off, the active steel of the cores is damaged to such an extent that at least 25% of new sheets must be added to restore it. Machines with significant damage to mechanical parts that cannot be repaired by the repair shop or enterprise are not accepted for repair. Such machines for their restoration may require significant costs in excess of the cost of a new machine. In addition, after repair, they will not have a sufficiently high operational reliability. In cases where the machine can be repaired without rewinding, pre-repair tests are carried out at idle for 30 minutes before disassembly. Before connecting the electric motor to the network, they check the free running of the rotor, the presence of lubrication in the bearing assemblies, measure the resistance and test the dielectric strength of the insulation. During pre-repair tests at idle, the currents in the phases of three-phase motors are measured, the condition of the mechanical part of the machine, the heating of the bearings, the magnitude of the vibration and a number of other operations are checked. An increase in no-load current in excess of the maximum allowable values may indicate a number of defects: an increase in the air gap, an axial displacement of the rotor relative to the stator, weak pressing of the core, a reduced number of winding turns as a result of an error during the previous repair.
In the process of disassembly, the air gap, the gaps in the bearings are measured.
Table. Air gaps for asynchronous motors
The unevenness of the air gap should not exceed 10% of the average value.
Electric motor malfunctions occur as a result of wear of parts and aging of materials, as well as in violation of the rules of technical operation.
Malfunctions of electric motors and possible causes of their occurrence.
In accordance with the Rules for technical operation in the system, it is planned - preventive repairs electrical equipment provide for two types of repairs: current and capital.
Current repairs are carried out at intervals (set by the chief power engineer) for all electric motors in operation. The typical scope of work for current repairs includes the following types of work: external inspection of the electric motor, flushing and relubrication of bearings and, if necessary, replacement of rolling bearings, checking and repairing fans, cleaning and blowing windings with compressed air, checking the state of fastening of the front windings, restoring varnish coatings these windings, checking and tightening all threaded fasteners, checking protective earthing, carrying out preventive tests.
Overhaul is carried out in the conditions of an electrical repair shop (ERTS) or a specialized repair enterprise (SRP). The scope of the overhaul includes the work provided for by the current repair. It also includes the following types of work: complete disassembly of the electric motor, checking of all components and parts and their fault detection, repair of frames and shield bearings, rotor and stator magnetic circuits, shafts, fans, rotors, elimination of local defects in the insulation of windings and connections, post-repair testing .
The frequency of major repairs of electric motors is not established by the Rules for technical operation. They are determined by the person responsible for the electrical facilities of the enterprise based on estimates of the overall operation of electric motors (duration) and local operating conditions.
Repair equipment management
The current repair of control devices consists of the following operations:
1. Partial disassembly, cleaning and washing of parts, hinges and axles.
2. Careful inspection of parts and assemblies in order to detect defects and malfunctions.
3. Replacement of defective parts and assemblies, elimination of violations of the correctness of their interaction.
4. Elimination of defects in contact surfaces (films, oxides, traces of erosion, soot, etc.) checking and adjusting the simultaneity of switching on, contact density, contact pressure.
5. Integrity checks and stripping of metal spatter of arc chutes.
6. Control of the absence of mechanical damage and restoration of damaged insulation
7. Verification of tightness of anchor and core.
8. Repair of mechanical components, lubrication of bearings and swivel joints.
9. Checks and adjustments of control and protection relays.
Overhaul is carried out with a complete disassembly of electrical appliances in specialized units with high level production mechanization.
When repairing magnetic starters with a thermal relay, attention is paid to the condition of these relays, the integrity of the heating elements. When replacing, only factory-made relay elements are used. Adjustment of the dips, as well as the simultaneity of touching the contacts of different poles, is carried out using shims that are laid between the contact holder and the traverse.
Adjustment of the contact pressure is carried out by measuring the compression of the contact springs. In many devices, this is done by changing the length of the springs using adjusting screws or nuts.
When repairing magnetic starters, the initial and final compression of the contact system is checked. The initial pressure is the force exerted by the contact spring at the point of initial contact. With insufficient initial pressure, welding of the contacts may occur, and with an increased pressure, the accuracy of the operation of the device will be disturbed. Pressing should be in the range of 50-60 kN. End push is the force exerted by the contact spring at the point of end contact when the starter is fully engaged. This value should be in the range of 90–110 kN. The initial and final contact compression of the devices is measured with a dynamometer. With the help of a loop and a dynamometer, the contact is pulled away from the contact holder. The beginning of the deformation of the spring is judged by the movement of a strip of thin paper previously placed between the contact holder and the contact. The tightness of the armature to the core is also adjusted. Irregularities in the joint of the ends of the magnetic circuit in the air gap leads to an increase in current, heating, noise and vibration. Therefore, only such irregularities in the joint are allowed, in which the total density of the anchor to the core is less than 70% of the cross-sectional area of the joint.
The interaction of all parts adjusted during the repair period is checked by turning on the magnetic starter several times by hand. Checking and testing of the magnetic starter is carried out according to the manufacturer's program. The results of post-repair test readings should not differ by more than 10% from factory test data.
Service power equipment
Before putting the newly installed equipment and the electric motor into operation or after installing the installation (unit), the place where the electric motor is installed is cleaned of debris, dust, dirt, then carefully inspect the internal parts, check for foreign objects in the machine, blow the electric motor with dry compressed air at a pressure not higher than 0.2 MPa.
They measure the insulation resistance, check the condition of the external bolted connections, and, if necessary, tighten them, inspect the supply cables and the tightening of the grounding bolts, check the compliance of the mains voltage with the voltage indicated on the electric motor shield, turn the rotor manually, measure the correct mating of the motor shafts and the drive mechanism.
Inspections of electric motors in operation, their control and protection systems are carried out according to the schedule approved by the chief power engineer of the enterprise. Inspection and testing of grounding is carried out daily (if there is a person on duty).
When inspecting electric motors, the temperature of bearings, windings, housings, load, and vibration are monitored. They check the cleanliness of the machine, the room, the cooling medium, the operation of the bearings, the serviceability of the guards.
Bearing temperature is measured using a thermometer. For rolling bearings, the temperature is measured on the outer ring when the machine is stopped. The maximum allowable temperature must not be exceeded.
When inspecting electric motors, they check with an ohmmeter whether there is a break in the grounding conductor of the cable.
The condition of the coupling or pulley is checked, paying special attention to the details of the coupling. Damaged rubber parts are replaced. A 500 V megohmmeter measures the insulation resistance of the stator windings of electric motors relative to the housing. The insulation resistance must be at least 0.5 Mohm at temperature.
Carefully inspect the board of clamps. In the presence of chips, cracks and charring of the surface, the board is replaced. Traces of overlapping with an arc are cleaned with a sandpaper, degreased with white - alcohol or acetone and covered with bakelite varnish or BF-2 glue.
Bearings after 4000 hours of work, but at least once a year, are washed with kerosene, and then filled with grease for 23 volumes of the bearing seat. Grease grades must be suitable for the operating conditions of the bearings.
To ensure the normal operation of the electric motor, it is necessary to maintain the voltage on the buses of the supply substation in the range from 100 to 105% of the nominal. For production reasons, the operation of the electric motor is allowed with voltage deviations from -5 to + 10% of the nominal.
At the temperature of the stator winding should not exceed by, and the rotor winding by the temperature of the cooling air.
During maintenance, the motor insulation resistance is periodically checked. For stator windings, the insulation resistance must be at least 10 MΩ, for rotor windings - 1.5 MΩ. If the insulation levels are not as specified, the windings are dried.
Service equipment management
Maintenance of electric devices up to 1000 V consists of periodic inspections, checks, cleaning and minor repairs. The frequency of maintenance is set by local regulations depending on the operating conditions, but not earlier than 1 time in 2-3 months.
During maintenance of electric devices with voltage up to 1000 V, the following types of work are carried out: cleaning, external and internal inspection, elimination of defects found and tightening of fastening threads; heating control of contacts, coils and other conductive elements; cleaning contacts from contamination, oxides, melting and adjustment from simultaneous closing and opening; replacement of fuses and faulty fuses; checking the electrical wiring.
Before starting the inspection, the voltage is turned off and measures are taken to exclude the possibility of its appearance on the main contacts and block contacts. Inspections of magnetic starters are carried out especially carefully, since the operation of technological equipment depends on their reliable operation.
The magnetic starter is switched on manually, they are convinced of the free movement of the movable system, the presence of contact between the movable and fixed contacts, the absence of distortions of the contact circuit, the serviceability of the contact springs. Springs that have lost their elastic properties or are damaged are replaced. When inspecting the arc chutes of magnetic starters, they remove soot with a cleaning cloth soaked in white spirit or gasoline. Splashes of metal on the gratings are cleaned off with a file.
The thickness of the ceramic-metal layer of contacts is measured. If the thickness of the ceramic-metal layer is less than 0.5 mm, the contacts are replaced.
Inspect the coil of the magnetic starter, make sure that there is no damage to the outer coating of the winding, as well as leaks of the top coat as a result of overheating. Check the tightness of the coil on the core.
Check the condition of the magnetic system and the short-circuited coil. The contact surfaces of the magnetic circuit are cleaned with a cleaning material. Corrosion on other surfaces of the magnetic starter is removed with sandpaper and covered with air-drying varnish. Check the heating element. In case of warping, metal burnout or coil shorting, the element must be replaced. The bimetallic plate is replaced in case of deformation and burning. After replacing the heating element or bimetallic plate, the relay is connected to a device or circuit that allows you to smoothly adjust the value of the test current. Next, inspect the insulating parts of the magnetic starters to make sure that there are no chips or cracks.
Fuses require constant monitoring, replacement of blown fuses and timely repair. Reliable and safe operation of electrical installations depends on their serviceability, correct selection of the insert. To speed up the selection and replacement of a blown insert, each fuse must have a clear figure for the rated current.
Security labor. Organization working places electrician
Proper organization of the workplace ensures rational movements of the worker and reduces to a minimum the time spent on finding and using tools and materials.
The mobile table is used when disassembling, washing and assembling various electrical equipment. It also serves as a vehicle for carrying cargo. The tabletop is lined with paper - laminated plastic with a steel corner edging. In the lower part of the table there is a metal shelf made of steel sheet 1.5 mm thick, designed for storing technological equipment and auxiliary materials.
The table is mounted on a wheel (with a low-resistance rubber rim) with rolling bearings. This provides good maneuverability and does not require much effort to move it.
The workbench consists of two pedestals with five drawers each with beds, in which locksmith and measuring tools, instruments, spare parts, electrical equipment are placed; drawers on frames with central constipation; the top drawer of the pedestal and the middle drawer for documentation, closed with a top lock; countertops; a desktop switchboard with an alternating voltage of 380 V connected to it, a voltage of 6,12,24,36,127,220 V and two signal panels for calling an electrician from 30 workplaces (30 points); a desktop locker with spare parts and a telephone for communication with plant subscribers. Cabinet - rack is designed to store large fixtures and spare tools used in the repair of electrical equipment. The upper compartments store various materials necessary for repairs.
The framework of a case — a rack is painted with gray enamel.
The mobile table is used for disassembling, washing and assembling various electrical equipment, and also serves as a vehicle for transporting goods. The table is mounted on wheels with bearings. This provides good maneuverability and does not require much effort to move it.
The duty electrician's portable bag is used for carrying tools and measuring equipment, fixtures, small parts for repairing electrical equipment in the workshop area.
The design of the chair - stool provides the most comfortable working posture. The seat can be easily and quickly raised or lowered.
The workplace should contain technical and accounting documentation, job description, as well as documentation on the organization and safety of work.
IN technical documentation includes: electrical circuits of the most complex machines, hoisting and transport equipment, a circuit diagram for supplying a workshop (site) with electricity, an electrical circuit for switchboards, etc.
Accounting documentation reflects the project of equipment and the work of an electrician. One of the types of such documentation is an operational (operational) log.
As binding document at the workplace of an electrician, there should be an instruction on labor safety for a shop electrician servicing electrical installations up to and above 1000 V.
Documentation on the organization of labor includes: a schedule of preventive examinations, a shift-hourly schedule and a map of the organization of work of the electrician on duty.
The workplace of an electrician must be designed in accordance with the requirements of technical aesthetics. The work clothes of an electrician should be comfortable, not restrict movement during work, and consist of a jacket, trousers and a beret (beret in a bright color - red, orange or brown).
Organizational And technical Events providing safety works V electrical installations
TO technical activities that ensure the safety of work in electrical installations include:
a) shutdown of the installation with the implementation of measures that exclude the erroneous supply of voltage to the place of work;
b) installation of fences and hanging posters;
c) checking the absence of voltage;
d) overlay grounding.
Disconnection can be performed using: manually operated switching devices, the position of the contacts of which is visible from the front side or determined by examining the panels from the rear side, opening the shields. Contactors or other remote devices after taking measures to eliminate the possibility of erroneous switching on (removing the auxiliary current fuses, disconnecting the ends of the closing coil).
On the drives of disconnectors, separators and control keys, as well as on the bases of the fuses, with the help of which voltage can be supplied to the place of work, posters are posted: “Do not turn on! People are working." Posters or warning signs should be posted on temporary fences: “Stop! Voltage".
Checking the absence of voltage between all phases and each phase in relation to the ground and the neutral wire on the part of the electrical installation that is disconnected for work is carried out by the permitter after warning posters are posted.
To protect the worker from possible electric shock, in case of erroneous voltage supply to the current-carrying parts of all phases of the disconnected. For the operation of the electrical installation, grounding is applied from all sides, from where voltage can be supplied, including as a result of reverse transformation.
Organizational activities include:
a) Issuing an order or order;
b) Permission to work;
c) supervision during work;
d) registration of breaks in work, transitions to another workplace;
e) registration of the completion of work.
Responsible for the safety of work are the persons issuing the work order: the responsible head of the robot is the person of the operational personnel who allows them to work; work producer; watching; workers in the team.
The right to issue orders for the production of work in electrical installations is granted to persons of the electrical personnel of the enterprise (head of the electrical department, head of the operation service, foreman), authorized to issue orders by order of the chief power engineer. These persons must have a qualification group V (in installations with a voltage of 1 kV - not lower than IV).
The complete completion of the work, indicating the date and time, is drawn up at the end of the order with the signature of the work foreman.
Allowing to work together with the responsible manager and the foreman (or supervisor) check the correctness of the preparation of the workplace and the composition of the team.
Supervision during work is carried out by the foreman (or supervisor), who should not be disconnected from the team.
Upon completion of all the work recorded in the order, the workplace must be inspected by the responsible manager, who, after the departure of the brigade, signs the order and hands it over to the operational staff.
Protective grounding
Grounding is the intentional connection of any part of an electrical installation to ground. Protective grounding is called, performed for the electrical safety of people and farm animals.
The principle of grounding protection is to reduce the voltage on the case when a current is shorted to it. When grounding is not available, the shorted case has a phase voltage with respect to ground. Touching it is just as dangerous as touching a live part. Grounding causes voltage redistribution. The case connected to ground electrode 2 will take its voltage equal to: U3=I3R3, where I3 is the fault current on this resistance, and will be many times less than in the absence of grounding.
Fault currents to the case are diverted to the ground through the ground electrode, i.e., a conductor or a group of conductors that are in direct contact with the ground. In electrical installations with voltage up to 1000 V with an isolated neutral, grounding devices must have a resistance of not more than R? 4 Ohm
With a total power of power sources of 100 kVA or less, they allow resistance R? 10 ohms
Protective nulling
Protective grounding, as a rule, is used in three-phase four-wire networks with a solidly grounded neutral with a voltage of up to 1000 V.
In these networks, grounding does not provide reliable protection.
To protect people from this voltage, it is necessary to reliably and quickly automatically disconnect the damaged section of the network. For this purpose, zeroing is arranged.
Grounding is the intentional connection of parts of an electrical installation to the grounded neutral of a transformer or generator. In the presence of grounding, the short-circuit current does not flow through the ground, but through the grounding metal conductors and, therefore, has a large value sufficient to burn out the fusible links or trip the protection. The short-circuit current acts on automata or fuse-links, which turn off the damaged section of the network and thereby eliminate dangerous potentials on the cases.
The fault current to the case does not flow through the ground, as was the case in the absence of grounding, but through the circuit: phase wire - neutral wire.
Zero is a wire connected to the grounded neutral of a transformer or generator.
The reliability of protective grounding depends on the resistance Rf and Rh of the circuit; phase wire - neutral wire.
For reliable and fast disconnection, it is necessary that the short-circuit current Ish exceeds the rated current of the fuse link
Ikz? To Inom, Where Inom is the rated current of the fuse-link;
K is the coefficient of reliability.
List used literature
1. V. B. Atabekov Repair of electrical equipment of industrial enterprises 1989 V.Sh. Moscow
2. A. S. Kokarev Electrician for the repair of electrical machines 1979 V.Sh. Moscow
3. Yu. V. Kornilov Maintenance of electrical installations of industrial enterprises 1986 V.Sh. Moscow
4. Yu. D. Sibikin Maintenance of electrical installations of industrial enterprises 1989 V.Sh. Moscow
5. Yu. D. Sibikin Handbook of a young worker on the operation of industrial enterprises, 1992 V.Sh. Moscow
6. G. P. Vartanov Electrician - repairman 1977 V.Sh. Moscow
7. A. A. Voronina Safety precautions when working in electrical installations 1974 V.Sh. Moscow
8. A. M. Gurzhiy Electrical engineering with the basics of industrial electronics Kyiv "Forum" 2002
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