Various types of electric motors are used in modern household and industrial equipment. Creating small home-made electrical appliances, masters often use the asynchronous type of motor. However, there are other varieties 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 should 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 stator of the electric motor is a fixed element of the mechanism. It is a magnetic drive and bearing structure of the motor. The DC motor has an inductor on the stator, and the AC-powered units have a working winding.
The stator consists of a core and a bed. The latter is a cast or welded case. The bed is most often created from aluminum or cast iron. The core has the shape of a cylinder. It is made of 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 parallel and isolated conductors.
The core is fixed to the bed with locking screws. This prevents it from turning.
Winding
The stator winding creates a magnetic field of a rotating type. In this case, the engine may have a different number of coils. They are interconnected. Coils are installed in the corresponding grooves. Such a design may consist of one or more turns of insulated conductors.
The stator winding can have a number of differences in different types of motors. This primarily concerns its isolation. This parameter is influenced by the magnitude of 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 entire coil is placed in the groove, but only its one side. In this case, the winding is called a single layer. If two sides of the coil are installed in the groove at once, then the design is called two-layer. The material for the stator winding is most often chosen a copper wire of circular cross section.
Inspection and Repair
After several years of operation, the master must check the electric motor. Repair after inspection may be ongoing or overhaul. This increases the reliability of the motor.
Overhaul involves complete disassembly of the structure. In this case, the rotor is removed, cleaned, and the stator is checked and inspected. If necessary, the wizard 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 engine cover removed. In accessible places, the windings are inspected.
The frequency and type of repair depends on the operating conditions of the equipment. This is affected by air pollution, ambient temperature, as well as the manufacturer's requirements. Overhauls are most often performed with a frequency of once every 3-5 years, and the current one - once or twice a year.
Is it worth it to rewind yourself?
When repairing the stator of an asynchronous electric motor , which is most often used today in household and industrial equipment, an insufficiently experienced craftsman may encounter a number of difficulties. In this case, he can contact the service department, where specialists will rewind for a fee in accordance with all the rules.
You should contact the professionals if the master does not even have minimal experience in repairing the electric motor. If there is not enough time and desire to perform such a procedure yourself, you should also entrust the rewinding to specialists. In this case, the costs will be determined on the basis of engine power and the number of revolutions per minute.
Rewinding of electric motors, the price of which is set by service centers today, 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 engines.
Engine disassembly
Repair of the stator of the electric motor must begin after disconnecting the device from the network. Next, the device is dismantled. Depending on the type and size of the motor, this can be done manually or using a crane.
Before starting repairs, the stator must be thoroughly cleaned of dirt accumulated on it over the years of operation. For this, special washing solutions are used. Sometimes it is necessary to perform a purge under pressure. To do this, use the same equipment as in car washes.
Only after this is the stator removed from the housing. With the help of a lathe (for industrial engines) or a chisel (for domestic motors), the frontal section of the winding is cut. Then the stator is heated to 200 ° C. This will soften the insulation and remove the winding. The grooves are thoroughly cleaned.
Inspection of the stator and its clearance 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, the average distance is calculated. Deviations of indicators in both directions should not be more than 10%.
If the gap is uneven, one-sided attraction of the rotor to the stator will be observed. The shaft and bearings will be subject to increased stress. Parallel branches and winding phases will be loaded differently. Noise, vibration will increase. If this deviation is not eliminated in time, the rotor will touch the stator. The engine will fail.
Next, the stator housing itself is inspected. Active steel should have a dense pressing. Also, the master must evaluate the strength of the installation in the strut channels. If the compact 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, the 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 in getinax wedges or put pieces of mica with varnish. In addition, when performing engine repairs, 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 make the whole operation with their own hands.
To do this, prepare special templates. A coil will be wound on them. When conducting unwinding, the master must remember (or take a picture) the number of turns in each of them. It is also required to measure the length and width of the formed skein.
The master can purchase a copper wire with exactly the same cross section as was 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. For this, a copper wire with a different cross-section and technical characteristics is purchased.
Wire and groove preparation
Rewinding a stator requires some preparatory work. Insert new insulation strips into the slots. They are cut out of electrical material with special indicators of thickness, dielectric strength and heat resistance. The required parameters of the insulating material can be set using the directory. 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 using special reference information. If the master remembers these parameters during unwinding, you can skip this step.
Winding
After all the preparatory work, the stator is rewound . In workshops, a special winding machine is used for this. It has a counter of the number of turns and special pads. They give the coils the desired shape. At home, you can create such pads yourself.
The work is performed on a table covered with a soft cloth. This will avoid damage to the insulating varnish. The coil must be threaded into the stator. Next, they lay the wire in the grooves, prying them alternately through a special gap.
You can guide the wires with a wooden tool that looks like a blunt knife. After laying the coil group, it is tied and a gasket is inserted. The system is fixed with the help of a special spike, which is driven along the entire length of the groove. Further, the same actions are performed with the next coil group.
Winding completion
The stator of the electric motor also requires the correct completion of repair work. Between the coils, intercoil insulation pads must be inserted. 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 the loops.
Form the frontal parts of the coil. It is poured with varnish and dried by heating to 150 ° C for several hours. The check is carried out after the engine has completely dried. Before this, it is also necessary to check the resistance between the windings and the casing.
Having considered what constitutes a stator of an electric motor , as well as its features, each master can perform maintenance and repair of such equipment.