Electric machines are used in almost all sectors of the economy. They perform a variety of functions. In order for this type of equipment to work stably, it is periodically repaired. Otherwise, downtime occurs, the company loses profits. Therefore, each enterprise plans and carries out the repair of electrical machines. How this procedure takes place, what features it is characterized by, will be discussed further.
Varieties
Each enterprise is engaged in the organization and repair of electrical machines, which are widely used in various activities. The equipment may differ in a lot of characteristics. Depending on the characteristics of such equipment, it is also planned to carry out appropriate maintenance procedures for the equipment.
Electric machines are widely used in modernindustries due to their high energy performance. They are also easy to maintain. An electrician for the repair of electrical machines, who is on the staff of the enterprise, must be able to perform maintenance of various types of equipment. There are many types of equipment presented. By appointment, it is divided into the following types:
- Generators. It is a technique that converts mechanical energy into electrical current. Their scope is wide. Such devices are installed at power plants, in cars, locomotives, ships and other objects. They are powered by turbines or internal combustion engines.
- Electric motors. They convert electrical current into mechanical energy. They are used to ensure the operation of various machines and mechanisms. This is the main part of the electric drive.
- Transformers. They change frequency, voltage. They can also be used to change the number of phases.
- Compensators. They generate reactive power and are used to improve the performance of energy sources and receivers.
- Amplifiers. Allows you to control objects of high power with the help of appropriate electrical signals.
- Signal converters. These are information and micromachines that create, recognize and convert electrical impulses. Information electric machines are used in automatic control systems. It is also a measuring, counting and decisive technique.
Repair and maintenance of electrical machines of each of the listed types of equipment is required to be carried out withestablished frequency. This is due to the conditions in which this or that technique works, as well as the design of the system.
Machines are divided into AC and DC devices. The first group includes synchronous, asynchronous and collector types. Transformers also fall into this category. They convert voltage and are used during measurements.
DC machines are used as generators or electric motors. They allow you to adjust the speed in a wide range.
In terms of power, electrical equipment is divided into:
- micromachines - up to 500 W;
- low power equipment - 0.5-10 kW;
- medium power equipment - 10-200 kW;
- high power installations - over 200 kW.
Types of faults
Repair of electric sewing machines, generators, micromotors and other similar devices may be required for various reasons. Electrical machines are damaged in most cases as a result of unacceptably long operation without proper repair or maintenance. Also, the reason may be a violation of the operating mode provided by the manufacturer.
Damages are divided into electrical and mechanical. The second group includes:
- smelting babbitt in plain bearings;
- destruction of cage, ball, ring or roller in rolling bearings;
- deformation of the rotor shaft (armature);
- formation of deep tracks oncollector surfaces;
- loosening the fastening of the starter poles or core to the frame;
- slipping or breaking of rotor cable ties;
- weakened movement of the anchor core;
- other.
The need to repair the windings of electrical machines can be caused by electrical damage. This, for example, can be a breakdown of the insulation of the case, a short circuit between the turns of the winding, a break in the winding conductors, broken contacts, and destruction of connections. Also presented types of damage include unacceptable reduction in insulation resistance due to aging, moisture or destruction.
Electrician repairing electrical machines should be well versed in the characteristic features of each type of breakdown. To determine the cause of the malfunction, the master must use different methods. The first one is a visual inspection. However, it is not always possible to detect a breakdown in this way. Many of them are hidden. It is only through appropriate testing that the cause of the failure can be determined.
Types of repairs
There are different types of repair of electrical machines. This keeps the machines running. Operating documents are supplied with the machine.
In them, the manufacturer specifies how often and what kind of repairs need to be carried out for specific equipment. Mandatory documentation that must be supplied with the machine includes:
- technical description of the mechanism;
- instruction, inwhich stipulates all the nuances of operation;
- machine form;
- maintenance manual;
- Regulations for installation work, commissioning, running-in and adjustment;
- technical data;
- list of spare parts, devices, tools;
- Statement of operational documents.
Most businesses today use a preventive maintenance system. It includes a set of measures aimed at maintaining equipment in working order.
The plan of such actions takes into account the features, the degree of wear of the equipment. Depending on the complexity of such a process, several varieties of preventive procedures are distinguished. This is the current, medium and major repairs of electrical machines. They have several characteristic features.
Current repairs include a minimum number of maintenance procedures. Wear parts are being replaced or upgraded. Also, the master can carry out adjustment work. Current repairs are carried out at the place of operation of the equipment.
Medium repairs involve the replacement of worn or damaged parts. At the same time, other parts of the electrical equipment require verification. If defects are found, they are corrected on the spot. This type of repair is the responsibility of the fixed and mobile services. In some cases, it is required to carry out major repairs of individual mechanisms or components. They can be transported to workshops for restoration.he alth.
During the overhaul, the machine is dismantled and fault-detected. All components must be replaced or repaired. Their condition is checked, after which the car is assembled in the reverse order. Adjustment and testing for correct operation. This type of repair is carried out by the company's stationary teams.
Defection
During the maintenance and repair of electrical machines, an action such as defecation is required. This is a preliminary stage of repair. In the course of fault detection, a list of faults, worn-out elements that require replacement is compiled. Based on this, an action plan is developed during the repair.
During fault detection, the object is inspected for faults, worn parts. Partial or complete disassembly of the electrical appliance may also be required. It depends on the type of equipment.
If a decision is made to carry out a visual inspection of the machine, such fault detection is often supplemented by appropriate tests. In some cases, this is quite enough to draw conclusions about the amount of upcoming repairs. However, this is not always possible. In some cases, only disassembling the device can reveal damage. Based on this, a schedule for future work is drawn up. Having prepared everything necessary, the master stops the equipment and performs the procedure for replacing defective parts.
To draw up a schedule for future work, a defect card is filled out. This includes all identifiedduring disassembly or testing, shortcomings in the operation of the unit. It is possible to perform the maintenance procedure with the least amount of time only on the basis of preliminary work. Repair of electrical machines in this case will be carried out as quickly as possible. Based on the fault map, an optimal sequence of actions for the foreman is drawn up. Usually the repair procedure includes several stages:
- Disassembly.
- Repair of windings.
- Mechanical repair.
- Assembly.
- Testing the operation of the assembled device.
Dismantling
Considering the technology of repairing electrical machines, it is worth paying attention to each stage of its implementation. After preliminary preparation, the master disassembles the device. The procedure for carrying out this action is determined by the design features of the equipment. The need to preserve the existing serviceable elements of the system is also taken into account. The degree of disassembly varies depending on the nature and extent of future repairs.
Before starting the repair, you need to make sure that all the necessary materials and new parts are available. They must correspond to the dimensions indicated in the data sheet of the device supplied by the manufacturer. Also, the components, parts and assemblies that are used during the repair must comply with the specified characteristics.
In most cases, the disassembly of electrical machines begins with the removal of the coupling half, which is located on the shaft. For this, hydraulic orhand tool. The second option is rarely used, since physical force is required to use this removable device. Only when repairing small units is it possible to use hand tools. If the machine is large, hydraulics must be used.
The rules for the repair of electrical machines indicate that before starting disassembly, you need to fix the coupling half with a sling on the hoist hook. Otherwise, it may fall. The center of the stop must match the center of the shaft.
Also, during the assembly process, you need to dismantle the casing, external and internal fans. It is required to unscrew the bolts, remove the bearing shield. Then you can get the rotor from the stator. The ends of the shaft are wrapped in cardboard so as not to damage them during the repair.
Coil repair
Repair of electrical machines and apparatus often involves updating the windings. These are conductors nested in the corresponding grooves, connected according to a certain scheme. This element of the system consists of coil groups, coils and turns. The last of these components consists of two conductors connected in series. They are located between oppositely charged poles. The number of turns is determined by the rated voltage of the device, and the cross-sectional area is determined by the current of the device.
The coil consists of several turns, which are stacked by the corresponding sides in the grooves. They are connected in series.
A coil group consists of several coils that are connected in series betweenyourself. Their sides are under two adjacent poles. The winding consists of several coil groups. They are connected in a certain pattern.
The master determines the type of winding and then rewinds it. The thickness of the wire, the material from which it is made, as well as the number of turns must correspond to the parameters that were selected by the manufacturer. For this, a preliminary calculation is made, a scheme is drawn up. Only after that it is possible to start repairing the windings of electrical machines. If you make a mistake, the technical characteristics of the device will be violated. It will not meet the specifications specified by the manufacturer, which is unacceptable.
Electrical repair
When planning the repair of electrical machines with direct current or alternating voltage, it is required to assess the correct functioning of the electrical part. So, in the course of this work, the short circuit of the winding to the body, between the turns, is eliminated. It may also require a complete replacement of the insulating material or winding.
If a breakdown occurs, a mechanical violation of the insulation, you need to knock out the wedges and lift the wires. The insulation is cut off from them, and then the damaged areas are wrapped again. For this, mica tape is used. Also, the insulation must be protected from above with a cotton cloth. Each layer is lubricated with a special adhesive type varnish. This is BT-95. The insulation is tightly tightened so that there are no air pockets between the layers.
If it is necessary to replace the general insulation, the winding is heated to 60-70 °C. Oldthe material is removed, and then the coil is tested for short circuits. Then the mica tape is wrapped around the entire coil. Subsequent turns are applied to the middle of the bottom layer.
You can also make new windings. If there is no wire of a suitable cross section, two thin wires are used. Their total cross section should be equal to the old wire. Most often, copper conductors are used. They are connected by soldering (diameter up to 1 mm) or electric welding (with a significant diameter). You can use soft and hard solders of the copper-phosphorus type. Acid cannot be used for these purposes.
Considering the features of the operation and repair of electrical machines, the following should be noted. To increase the resistance of the new winding to adverse conditions, it is impregnated with a special varnish. To do this, it is dried in a special apparatus at a temperature of 120 ° C. Then the heating is reduced to the level of 60-70°C. After wetting the winding with a special compound, you need to wait until the air bubbles cease to stand out. Then the winding is dried again. A layer of topcoat type varnish is applied on top.
Mechanical Repair
When repairing electric sewing machines, generators, motors and other types of appliances, it is worth considering the maintenance procedure for the electrical part. In the course of this work, it is required to restore the working surfaces of collectors, shafts, slip rings. Defects in bearing shields are also eliminated.
The shaft repair procedure requires special attention. This is one of the most important stages. In most cases, the shaft cannot be separated from the base. This circumstancesomewhat complicates the repair process. Defects can be eliminated by grinding and turning on turning equipment. The shaft can be reground to a smaller diameter. The master can perform welding or plating and subsequent processing.
If it is necessary to perform the restoration of the functions of the bearing seats, the bushings are pressed in or surfacing is carried out. Next, boring is made to the required size. If there are small cracks, they are welded by cold welding. Staple stitching may be applied.
In DC electrical machines, a common failure is the wear of the collector, which damages the working surface. It is repaired or replaced with a new unit. If the mechanism belongs to the group of short-circuiting, the side ribs of the ring often wear out here, the gap between it and the shaft increases.
Recovery of the collector is a complex procedure. In this case, the repair of electrical machines suggests that the insulation requires milling. This work is performed on a special machine. If the shape of the collector is broken, it is stretched, tracked and polished. Then polishing is carried out.
Assembly of equipment
During the repair of electrical machines, it is important to properly assemble. It is carried out in reverse order. This procedure depends on the type of equipment, features of its design.
First, bearing caps are put on the shaft, grease is put into the grooves. The ball bearing is heated and placed on the shaft. The spring ring is inserted into the groove. The rotor is inserted into the stator using a suitableequipment.
The shields are installed on the bearings after the lubrication has been added. Install the lock of the bed and tighten the bolts. The gap between the stator and the rotor is checked with a feeler gauge. The winding is connected to a power source. The terminal box is fixed with bolts. After that, the engine is run in at idle for half an hour.
Assembly scheme may differ, but only slightly. The disassembly and assembly procedure is described in the relevant documentation supplied by the manufacturer.
Testing
Repair of electrical machines is completed by testing. First, the equipment is inspected externally. The air gaps between the cores are measured. The insulation resistance is measured on the case and between the phases of the windings.
At idle, the ohmic resistance is determined. Next, the transformation ratio is determined if a phase rotor is installed in the machine. If everything is in order, the tests are carried out at idle. In this mode, current indicators are measured by phases.
If the motor belongs to the short-circuited group, the starting current and its multiplicity are measured. The electrical strength of the insulation is also measured on the turns, relative to the housing, and also between phases. A short circuit test is carried out. Under load, the degree of heating of the device is checked.
All test results are recorded in the appropriate statement. If everything is in order, a conclusion is made about the possibility of using the equipment in the course of the enterprise's activities.
