Motor stator winding winding turn-to-turn short-circuit hazard and inspection judgment skills
Winding short-circuit faults usually have two types: phase-to-phase short circuit and turn-to-turn short circuit. The turn-to-turn short circuit includes a short circuit between the coils of each pole phase group, a short circuit between the coils in one pole phase group, and a short circuit between the turns in one coil. Phase-to-phase short-circuit faults typically have a short-circuit between the winding ends and a short-circuit between the upper and lower coils in the slot. The reason for the phase-to-phase short circuit is that the phase-to-phase insulation size does not conform to the regulations, the insulation pad itself is defective, the interlayer gasket is biased, or the wire is damaged. In addition, the insulation damage of the winding connection wire or the lead wire bushing may also cause a phase-to-phase short circuit.
Motor overload, overvoltage, single-phase operation, poor wire insulation materials, etc. will cause short circuit between turns. In particular, the thermal mechanical strength of the polyester enameled wire is poor. When the immersion lacquer is poor and the sturdy integral is not formed between the crepe, a large amount of external dust will accumulate in the gap of the wire, and the wire will vibrate and rub against each other under the action of electromagnetic force. The dust stuck in the gap acts as an "abrasive". After a long time, the wire is insulated and broken to form a short circuit between turns.
(1) Short-circuit fault repair of the pole phase group at the end of the coil. The triangular insulating pad of the inter-group pad between the coil ends is soldered when soldering, forming a tin flow or burr when cooling, punctures the insulating pad, or the solder burns the insulating pad, which will cause the interphase insulating pad Partial breakdown due to loss of insulation causes a short circuit between the pole phases. The repair method is to heat the coil, soften the insulation, then use the cable management board to open the coil between the coil sets, reinsert the new insulation mat, and finally paint.
(2) Repair of winding short-circuit fault caused by insulation damage of winding end connection line or bridge line. Since the insulating sleeve of the connecting wire is crushed, or the plastic sleeve is softened after drying, and does not have an insulating effect, a short circuit between the pole phases is caused. When repairing, use the cable management board to open the connecting line, clean the old casing, and then insert the new insulating sleeve or wrap it with insulating tape. When the coils cross the bridge line, coil short-circuit faults may occur due to improper weaving or shaping. The solution is also to soften the coil heating, use the cable management board to open the bridge line, and increase the insulation.
(3) Repair of the winding end wire short circuit. The short-circuit at the end of the winding is caused by poor dipping and the vibration of the wire is worn and insulated. After finding the short-circuit coil by the voltage drop method, in order to quickly find the short-circuit point of the coil, it is recommended to connect the phase coil to the single-phase low voltage and connect it to the two ends of the short-circuit coil with an AC voltage meter. The bamboo plate gently shakes the short-circuit coils. When the voltmeter pointer suddenly rises to the normal value, it indicates that the short-circuit point has been separated, and the insulation pad is used to pad the place, and then the paint is insulated.
(4) Repair of short circuit between two layers of coils. The double-layer coils have interlayer short-circuit between the upper and lower layers, which is caused by the poor insulation quality of the interlayer or the inconsistent size of the interlayer insulating spacers during the weaving, the unevenness and displacement of the interlayer insulating spacers. The short circuit between the upper and lower layers in the processing tank or the inter-turn short circuit of the upper and lower coils itself is the same as the method for handling the ground fault described above. If the removed coil is multiplexed by the wrapped insulation, it is also checked whether the intact coil is also damaged by the inter-turn insulation during the removal process, and the simple transformer device is used for inspection.
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