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 profit. Therefore, each company plans and carries out repairs of electrical machines. How this procedure occurs, what features it is characterized by will be considered further.
Varieties
Each enterprise is engaged in the organization and repair of electrical machines, which are widely used in various types of activities. The equipment may differ in weight characteristics. Depending on the characteristics of such equipment, it is planned to carry out appropriate maintenance procedures for the equipment.
Electric machines are widely used in modern industry due to their high energy performance. They are also easy to maintain. An electrician for the repair of electrical machines, which is on the staff of the enterprise, must be able to perform maintenance on various types of equipment. There are many types of equipment presented. By appointment, it is divided into the following types:
- Generators. This is a technique that converts mechanical energy into electric current. Their scope is wide. Such devices are installed in power plants, in cars, diesel locomotives, on ships and other objects. They are driven 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.
- Converters. They change the frequency, voltage. They can also be used to change the number of phases.
- Compensators. Reactive power is generated and used to improve the performance of energy sources and receivers.
- Amplifiers They allow you to control objects of high power using appropriate electrical signals.
- Signal converters. These are information and micromachines that create, recognize and transform electrical impulses. In automatic control systems, information electric machines are used. It is also a measuring, calculating and solving technique.
Repair and maintenance of electrical machines of each of the listed types of equipment is required to be carried out at specified intervals. This is explained by the conditions in which this or that equipment operates, as well as the system design.
Machines are divided into AC and DC devices. The first group includes synchronous, asynchronous and collector types. Also in this category are transformers. They convert voltage and are applied during measurements.
DC machines are used as generators or electric motors. They allow you to adjust the speed over 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 work without proper repair or maintenance. Also, the cause may be a violation of the operating mode provided by the manufacturer.
Damage is divided into electrical and mechanical. The second group includes:
- smelting of babbit in sliding bearings;
- destruction of the cage, ball, ring or roller in the rolling bearings;
- deformation of the rotor shaft (anchor);
- the formation of deep tracks on the surface of the collectors;
- weakening the fastening of the poles or core of the starter to the frame;
- sliding or tearing of cable ties of rotors;
- weakening the movement of the core of the anchor;
- other things.
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 casing, a short circuit between the turns of the winding, a break in the conductors of the winding, breaking contacts, breaking connections. Also presented types of damage include an unacceptable decrease in insulation resistance due to aging, moisture or destruction.
An 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 far from always that a breakdown can be detected in this way. Many of them are hidden. Only through appropriate tests can the cause of the malfunction be determined.
Types of Repair
There are different types of repair of electrical machines. This allows you to maintain the machine in working condition. Operation documents are supplied with the machine.
In them, the manufacturer stipulates how often and what kind of repair should be carried out for specific equipment. The mandatory documentation that must be delivered with the machine includes:
- technical description of the mechanism;
- instruction, which stipulates all the nuances of operation;
- form for cars;
- maintenance instruction;
- instructions for installation, commissioning, running-in and adjustment;
- technical details;
- statement of spare parts, devices, tools;
- statement of operational documents.
Most enterprises today use a preventative maintenance system for repairs. It includes a set of measures aimed at maintaining equipment in working condition.
The plan of such actions takes into account the features, the degree of wear of the equipment. Depending on the complexity of this process, several varieties of planned preventive procedures are distinguished. This is the current, medium and overhaul of electrical machines. They have several characteristic features.
Maintenance includes a minimum number of maintenance procedures. Replace or update wear parts. Also, the master can carry out adjustment work. Maintenance is carried out at the place of operation of the equipment.
Medium repair involves replacing worn or damaged parts. However, the remaining parts of the electrical equipment require verification. If malfunctions are found, they are corrected on site. This type of repair is the responsibility of the fixed and mobile services. In some cases, overhaul of individual mechanisms or components is required. They can be transported to workshops to restore their performance.
During the overhaul, the machine is disassembled and faulted. All components must be replaced or repaired. Their condition is checked, after which the car is assembled in the reverse order. Adjustment and testing of correct operation are carried out. This type of repair is carried out by stationary teams of the enterprise.
Defect
During the maintenance and repair of electrical machines, an action such as defecation is required. This is a preliminary repair step. During the defect, a list of faults, worn-out items that require replacement is compiled. Based on this, an action plan is developed during the repair.
During the detection, the object is inspected for malfunctions, 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 conduct a visual inspection of the machine, such a defect is often supplemented by appropriate tests. In some cases, this is enough to draw conclusions about the amount of upcoming repair work. However, this is far from always possible. In some cases, only by disassembling the device can damage be detected. Based on this, a schedule of future work is drawn up. Having prepared everything necessary, the master stops the equipment and performs the procedure for replacing faulty parts.
In order to schedule future work, a defect map is filled out. All the defects in the operation of the unit identified during disassembly or testing are added here. The service procedure can be carried out with the least expenditure 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 defect card, the optimal sequence of actions of the wizard is compiled. Typically, the repair procedure includes several stages:
- Disassembly.
- Winding repair.
- Repair of the mechanical part.
- Assembly.
- Testing the operation of the assembled device.
Disassembly
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 this action is determined by the design features of the equipment. It also takes into account the need to maintain existing operational elements of the system. The degree of disassembly varies depending on the nature and extent of future repairs.
Before starting repairs, you need to make sure that you have all the necessary materials and new parts. They must correspond to the dimensions indicated in the data sheet of the device supplied by the manufacturer. Also, components, parts and assemblies that are used during the repair must comply with the specified characteristics.
In most cases, disassembly of electrical machines begins with the removal of the coupling half, which is located on the shaft. For this, a hydraulic or manual tool is used. The second option is rarely used, because to use this removable device you need to use physical force. Only when repairing small units is it possible to use a hand tool. If the machine is large-sized, hydraulics must be used.
The rules for the repair of electrical machines indicate that before disassembling, you must fix the coupling half with a sling on the hoist hook. Otherwise, it may fall. The center of the stop should coincide with the center of the shaft.
Also during the assembly process, it is necessary 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 out of the stator. The ends of the shaft are wrapped in cardboard so as not to damage them during the repair.
Winding repair
Repair of electrical machines and apparatuses often involves updating the windings. These are conductors embedded in the corresponding grooves, connected in a certain pattern. This element of the system consists of coil groups, coils and turns. The last of these components is two conductor connected in series. They are located between the uncharged 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 laid by the respective sides in the grooves. They are connected in series.
The coil group consists of several coils that are connected in series with each other. Their sides are under two adjacent poles. The winding consists of several coil groups. They are connected in a certain pattern.
The wizard 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 should correspond to the parameters that were selected by the manufacturer. For this, a preliminary calculation is made, a diagram is drawn up. Only after this can you 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, and this is unacceptable.
Repair of electrical parts
When planning repairs of electric machines of direct current or alternating voltage, it is required to evaluate the correct functioning of the electrical part. So, in the course of this work, the closure of the winding on the housing, between the turns, is carried out. A complete replacement of the insulation material or winding may also be required.
If there is a breakdown, a mechanical violation of the insulation, you need to knock out the wedges and raise the wires. The insulation is cut off from them, and then the damaged areas are wrapped again. For this, Mikalenta is used. Also, insulation must be protected with a cotton cloth on top. Each layer is lubricated with a special varnish adhesive type. This is a VT-95. The insulation is firmly 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. Old material is removed and then the coil is tested for short circuits. Further mikalentu wrapped throughout the coil. Subsequent turns are applied to the middle of the lower layer.
You can also make new windings. If there is no wire of suitable cross-section, two thin conductors are used. Their total cross-section should be equal to the old wire. Most often used copper conductors. They are connected by soldering (diameter up to 1 mm) or electric welding (with a significant diameter). You can apply soft and hard solders of copper-phosphorus type. Acid cannot be used for these purposes.
Considering the features of 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 a level of 60-70 ° C. After wetting the winding with a special composition, you need to wait until the air bubbles cease to stand out. Then the winding is dried again. A coating layer of varnish is applied on top.
Mechanical repair
When repairing electric sewing machines, generators, motors and other types of devices, it is worth considering the procedure for servicing the electrical part. In the course of this work, it is required to restore the working surfaces of the collectors, shafts, slip rings. Defects in bearing shields are also eliminated.
Particular attention is required to repair the shaft. This is one of the most critical stages. In most cases, the shaft cannot be separated from the base. This circumstance somewhat complicates the repair procedure. Defects can be eliminated by grinding and grooving on turning equipment. The shaft can be regrind to a smaller diameter. The craftsman can perform surfacing or metallization and subsequent processing.
If necessary, perform the restoration of the functions of the bearing seats, the bushings are pressed in or surfaced. Then a boring is made to the required size. If there are small cracks, they are brewed by cold welding. Bonding firmware may be used.
In DC electric machines, frequent wear and tear is manifold wear, which damages the work surface. It is being repaired or replaced with a new unit. If the mechanism belongs to the group of short-circuits, the side ribs of the ring often wear out here, the gap between it and the shaft increases.
Collector recovery is a complex process. In this case, repairing electrical machines suggests that insulation requires milling. This work is performed on a special machine. If the shape of the collector is violated, it is pulled, priced and polished. Then polished.
Equipment assembly
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, its design features.
First, bearing caps are put on the shaft, grease is put in the grooves. The ball bearing is heated and mounted on the shaft. The snap ring is inserted into the groove. The rotor is introduced into the stator using appropriate equipment.
Shields are mounted on bearings after lubrication. Install the bed lock and tighten the bolts. The probe checks the clearance between the stator and the rotor. The winding is connected to a power source. The terminal box is bolted. .
, . , .
. . . .
. , . , . .
If the motor belongs to the group of short-circuited, the inrush current is measured and its multiplicity. It also measures the dielectric strength of the insulation on the turns, relative to the housing, as well as between the phases. A short circuit test is being conducted. 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 equipment in the course of the enterprise.