What are the training and learning methods for motor repair?

Generally, many people will learn motor maintenance, but at this time, you still need to master certain methods to learn well. So do you know what kind of training is available? The following is compiled for you by the editor of SmartView Motor repair training and learning, I hope it can help you.

Training and learning of motor repair 1. Fault phenomenon

The casing is electrified, the control circuit is out of control, and the winding is short-circuited and heated, causing the motor to fail to operate normally.

2. Causes

The insulation resistance of the windings decreases due to moisture; the motor is overloaded for a long time; harmful gases corrode; metal foreign matter invades the inside of the windings and damages the insulation; the insulation is damaged when rewinding the stator windings. The iron core; the end of the winding hits the end cover base; the friction between the stator and the rotor causes insulation burns; the insulation of the lead wire is damaged and collides with the shell; overvoltage (such as lightning strikes) causes insulation breakdown.

3. Inspection method

(1) Observation method. Visually inspect the ends of the windings and the insulation in the trunking to see if there are any signs of damage or charring. If there are any, it is the grounding point.

(2) Multimeter inspection method. Check with the low resistance setting of the multimeter. If the reading is very small, it is grounded.

(3)Megohmmeter method. Use different megohmmeters according to different levels to measure the insulation resistance of each set of resistors. If the reading is zero, it means that the winding is grounded. However, if the motor insulation is affected by moisture or breaks down due to an accident, it needs to be determined based on experience. Generally speaking, When the pointer swings unsteadily at ?0?, it can be considered to have a certain resistance value.

(4) Light test method. If the test light is on, it means the winding is grounded. If sparks or smoke are found somewhere, it is the winding ground fault point. If the light is dimly lit, the insulation has ground breakdown. If the light does not light up, but sparks appear when the test rod is grounded, it means that the winding has not broken down, but is only seriously affected by moisture. You can also use hard wood to tap lightly on the edge of the shell. When you tap on a certain place and wait for it to turn off and on, it means that the current is on and off, and that place is the grounding point.

(5)Current burning method. Using a voltage regulating transformer, after connecting to the power supply, the grounding point will heat up quickly, and the place where the insulation smokes is the grounding point. Special attention should be paid to that small motors should not exceed twice the rated current for no more than half a minute; for large motors, the rated current should be 20-50 or gradually increase the current, and cut off the power immediately when the ground point starts to smoke.

(6) Group elimination method. For cases where the grounding point is inside the iron core and the burning is severe, the burned copper wire and the iron core are fused together. The method used is to divide the grounded one-phase winding into two halves, and so on, and finally find the grounding point.

In addition, there are high-voltage test methods, magnetic needle exploration methods, power frequency vibration methods, etc., which will not be introduced here.

4. Treatment method

(1) If the winding is damp and causes grounding, it should be dried first. When cooled to about 60-70℃, insulating paint should be poured on it and then dried. .

(2) When the insulation at the end of the winding is damaged, re-insulate the grounding point, paint it, and then dry it.

(3) When the winding grounding point is in the slot, the winding should be rewinded or some winding components should be replaced.

How to maintain the motor 1. Preparation work before motor installation

A motor that is newly installed or has been idle for more than three months must have its safety and electrical performance checked before use. and mechanical performance inspection to ensure safe and reliable operation of the motor.

1. Check the insulation resistance of the motor winding. Open the junction box. Use a megohmmeter above 500V to measure the insulation resistance between the winding and the base. The normal resistance should be >5M ohms. Remove the connecting piece of the terminal block and measure the insulation between the winding phases. The normal resistance value should be >10M ohms. If during the above measurement process, the resistance value is seriously low at one time, the motor should be disassembled to find the reason. If there is no fault point, it means that the insulation performance of the motor is reduced due to moisture. It should be baked to drive away moisture. It cannot be installed and used until the insulation is qualified.

2. Measure the resistance of the three-phase winding. Observe whether the resistance values ??are the same. If the resistance values ??are significantly different, check whether the motor winding leads have poor contact or other reasons.

3. Check whether the mechanical part of the motor is qualified.

Turn the rotating shaft by hand to check whether it is flexible and whether there is abnormal friction, jamming, shaft shifting and abnormal noise. At the same time, check whether all components are complete, whether the solid screws are tightened, and whether the coupling or pulley is installed and corrected.

2. Motor installation and trial operation

Before wiring the motor, first check whether the control circuit and protection circuit are normal, whether the fuse is appropriately selected, and the connections between the control appliances Are the contacts firm? If it is normal, connect the motor power supply and start it without load, and observe whether the motor running direction meets the equipment requirements. If the direction of rotation is opposite, just swap any two power incoming wires on the motor wiring board. After the start-up test is normal, connect the motor to the load for trial operation, and check whether its operating current is normal. If the current is too large, stop the machine for inspection.

If the motor does not rotate or rotates at a very low speed after loading, or there is an abnormal hum, the power should be cut off immediately. If the power is on for a longer time, it is very likely to burn the motor windings and even damage the control circuit and Damage to equipment, generally in this case, the mechanical reason is overload or jamming, and the electrical reason is phase failure. At this time, the cause of the fault should be carefully checked and the test run can be restarted only after the fault is eliminated.

3. Maintenance during motor operation

Whether the motor is running normally can be judged from the sound, speed, temperature, working current and other phenomena of the motor. If a running motor has leakage, a sudden decrease in speed, severe vibration, abnormal noise, overheating and smoke, or the control electrical contacts are igniting and smoking, the power should be cut off immediately for maintenance. Listen to the sound the motor makes when it is running. If you find a loud buzzing sound, it means either the current is high or it is running out of phase. If there is abnormal friction sound, it may be that the bearing is damaged and the chamber is swept. If there is a slight abnormal sound, you can use a wooden stick or long-rod screwdriver, one end to the motor bearing, and the other end close to your ear, and carefully identify whether the sound is abnormal. If there is an abnormal sound, it means there is a problem with the bearing, and it should be replaced in time to avoid damage to the bearing cage, causing friction between the rotor and the stator, and burning the stator winding of the motor. Observe whether the control electrical contacts and motor wiring contacts are loose, abnormally heating up or sparking, and whether the insulation is aging. Is there any abnormal vibration or sound in the contactor, and is it sparking after the contacts are closed? If such problems are found, they should be dealt with as soon as possible to avoid accidents.

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