Different types of electric motors are used in modern household and industrial appliances. Creating small home-made electrical appliances, craftsmen most often use an asynchronous type of motor. However, there are other types of drives that are used in industrial production. All presented mechanisms have a rotor and a stator of an electric motor.
Even the most reliable designs require maintenance or repair over time. Therefore, every electrician who works with such equipment must know the rules for such a procedure. Even at home, you can rewind and check the stator, as well as evaluate the gap between it and the rotor.
What is a stator
The motor stator is a fixed element of the mechanism. It is a magnetic drive and a supporting structure of the motor. A DC motor has an inductor on the stator, and AC-powered units have a working winding.
The stator consists of a core and a frame. Lastis a body of cast or welded production. The bed is most often created from aluminum or cast iron. The core is in the form of a cylinder. It is made from electrical steel. Sheets of material are first fired and then insulated with varnish. There are grooves inside the core. They are designed for laying the stator winding. This is necessary to attenuate eddy currents. The stator winding consists of a series of wires connected in parallel and insulated.
The core is secured to the frame with set screws. This prevents it from turning.
Wrapping
The stator winding creates a rotating type magnetic field. In this case, the engine can have a different number of coils. They connect with each other. Coils are installed in the corresponding grooves. This design may consist of one or more turns of insulated conductors.
The stator winding may have a number of differences in different types of motors. This primarily concerns its isolation. This parameter is affected by the voltage during operation, the shape and size of the groove, the limiting temperature of the winding, as well as its type.
It happens that not the whole coil is placed in the groove, but only one side of it. In this case, the winding is called single-layer. If two sides of the coil are installed in the groove at once, then the design is called two-layer. The most common material for the stator winding is round copper wire.
Inspection and repair
After several years of operation, the master must check the electric motor. Repair after inspectionmay be current or capital. This increases the reliability of the motor.
Overhaul involves a complete disassembly of the structure. In this case, the rotor is removed, cleaned, and the stator is checked and inspected. If necessary, the master eliminates the identified defects. Also, after all inspections, replacement of faulty parts, the master tests the operation of the equipment.
In some cases, it is not necessary to completely disassemble the electric motor. The current repair involves only cleaning and blowing the stator with the rear cover of the engine removed. In accessible places, the windings are inspected.
The frequency and type of repair depends on the operating conditions of the equipment. This is influenced by air pollution, ambient temperature, as well as manufacturer's requirements. Major repairs are most often carried out every 3-5 years, and the current one - once or twice a year.
Should I rewind myself?
When repairing the stator of an asynchronous electric motor, which is most often used today in household and industrial appliances, an insufficiently experienced master may encounter a number of difficulties. In this case, he can contact the service departments, where specialists will perform rewinding in accordance with all the rules for a fee.
You should turn to professionals if the master does not have even minimal experience in repairing an electric motor. If there is not enough time and desire to perform a similar procedureindependently, you should also entrust rewinding to specialists. In this case, the cost will be determined based on the power of the engine and the number of revolutions per minute.
Rewinding electric motors, the price of which is currently set by service centers, will cost about 2-4 thousand rubles. However, for more powerful engines, prices increase significantly. The procedure can reach 135 thousand rubles. for rewinding large industrial motors.
Engine disassembly
Repair of the motor stator must be started after disconnecting the device from the mains. Next, the device is dismantled. Depending on the type and dimensions of the motor, this can be done manually or with a crane.
The stator must be thoroughly cleaned of dirt that has accumulated on it over the years of operation before starting repairs. For this, special cleaning solutions are used. Sometimes a pressure purge is required. To do this, use the same equipment as in car washes.
Only after that the stator is removed from the housing. Using a lathe (for industrial engines) or a chisel (for household motors), the frontal section of the winding is cut off. Then the stator is heated to 200ºС. This will soften the insulation and remove the winding. The grooves are thoroughly cleaned.
Inspection of the stator and its gap between the rotor
After removing the insulating coupling half, it is required to measure the gap between the rotor and the stator of the electric motor. Based on the data obtained, theaverage distance. Deviations of indicators in both directions should not exceed 10%.
If the gap is uneven, there will be a one-sided attraction of the rotor to the stator. The shaft and bearings will be subjected to increased stress. Parallel branches and winding phases will be loaded differently. Noise and vibration will increase. If this deviation is not corrected in time, the rotor will touch the stator. The engine will fail.
Next, the stator housing itself is inspected. Active steel must have a tight pressing. Also, the master must evaluate the strength of the installation in the channels of the spacers. If the pressing is not strong enough, the core sheets begin to vibrate. Such a process leads to the destruction of the insulation between them. As a result, local overheating of the steel itself, as well as the windings, is determined in the engine.
To increase the density of steel sheets, the master must hammer getinax wedges or place pieces of mica with varnish. In addition, when repairing the engine, it is necessary to inspect other mechanisms (rotor, bearings).
Stator rewind
Rewinding electric motors will require a certain amount of knowledge and skills. The price of such a procedure is quite high. Therefore, many masters decide to do the whole operation with their own hands.
For this you need to prepare special templates. A coil will be wound on them. When unwinding, the master must remember (or photograph) the number of turns in each of them. It is also required to measure the length andthe width of the formed skein.
The master can purchase copper wire with exactly the same cross section as used in the engine. The electromechanical characteristics of the insulating material must also be identical. If desired, the master can set new indicators of power and rotor speed. To do this, a copper wire with a different cross section and technical characteristics is purchased.
Preparation of wire and grooves
Rewinding the stator requires some preparatory work. New insulation pads must be inserted into the grooves. They are cut from an electrical material with special indicators of thickness, dielectric strength and heat resistance. The required parameters of the insulating material can be set using the reference book. To do this, you need to know the basic parameters of the engine.
Next, you need to calculate the required number of turns of the winding and the wire itself. The correct type of winding can be determined according to the dimensions of the stator with the help of special reference information. If the master memorized these parameters during unwinding, you can skip this step.
Wound
After carrying out all the preparatory work, the stator is rewound. In workshops, a special winding machine is used for this. It has a counter for the number of turns and special pads. They give the coils the desired shape. At home, you can create these pads yourself.
Work is done on a table covered with a soft cloth. This will allowavoid damaging the insulating varnish. The coil must be threaded inside the stator. Next, the wire is laid in the grooves, prying them alternately through a special gap.
You can guide the wires with a wooden tool that looks like a dull knife. After laying the coil group, it is tied up and a gasket is inserted. The system is fixed with a special peg, which is driven in along the entire length of the groove. Further, the same actions are performed with the next coil group.
Finish winding
The motor stator also requires proper completion of repairs. Between coils it is necessary to insert intercoil insulating gaskets. They look like strips of special material. Next, you need to tie the back of the stator with a special rope. It is crocheted through loops.
Form the frontal parts of the coil. It is filled with varnish and dried by heating up to 150ºС for several hours. The check is carried out after the engine has completely dried. Before that, you must also check the resistance between the windings and the case.
Having considered what the stator of an electric motor is, as well as its features, each master can service and repair such equipment.
