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Analysis of Winding Ground Fault Maintenance

time:2021/1/6   source:华天电力  reading:274 time

Motor fault maintenance analysis Winding is an integral part of the motor. Aging, moisture, heat, erosion, foreign matter intrusion, and external force impact will cause damage to the winding. Motor overload, undervoltage, overvoltage, and phase loss operation can also cause winding failure , Winding faults are generally divided into winding grounding, short circuit, open circuit, and wiring errors. Now the fault phenomenon, cause and inspection method are explained separately.


Refers to the grounding caused by the insulation damage between the winding and the iron core or the casing.


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


Moisture of the windings reduces the insulation resistance. Tianjin DC motor repairs the motor for long-term overload operation, harmful gas corrosion, metal foreign objects invade the windings and damage the insulation, and the insulation damages the core when rewinding the stator windings, and the ends of the windings touch the end cover base, stator and rotor Friction causes insulation burns, lead wire insulation damage and collision with the shell, and overvoltage (such as lightning strike) causes insulation breakdown.


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Inspection Method


1. Observation method


Observe whether there is damage and burnt traces by visually inspecting the ends of the windings and the insulation in the wire slot. If there is, it is the grounding point.


2. Multimeter inspection method


Use a multimeter to check the low-resistance gear. If the reading is small, it is grounded.


3. The megohmmeter method


Choose different megohmmeters to measure the insulation resistance of each group of resistors according to different levels. If the reading is zero, it means that the winding is grounded, but the motor insulation is damp or broken due to an accident. It needs to be judged based on experience. Generally speaking The pointer swings irregularly at "0", and it can be considered that it has a certain resistance value.


4. Light test method


If the test light is on, it means that 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 a ground breakdown. If the light does not light, but the test rod is grounded Sparks appear, indicating that the winding has not been broken down, but is seriously damp. You can also tap hardwood on the edge of the shell. When you knock it to a certain place and wait for it to turn off and turn 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 quickly heats up, and the place where the insulation emits smoke is the grounding point. Special attention should be paid to the small motor not to exceed twice the rated current, and the time does not exceed half a minute. 20%-50% of the rated current or gradually increase the current, and immediately cut off the power when the grounding point just smokes.


6. Group elimination method


For the grounding point in the iron core and the burning is severe, the burnt 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.

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