Ac motor & # 8203; Winding short-circuit winding short-circuit fault is refers to the winding turns or between different winding insulation damage and the formation of a short circuit phenomenon. After the failure, electric timing smoke (Short circuit when the number of turns rarely, don't smoke), unbalanced three phase current, the motor noise and vibration during operation, serious when motor can't start. Are: the cause of winding short-circuit motor overload, often too much electricity; Single phase operation; Power supply voltage change is too big; Winding mechanical damage, as well as the manufacture or repair technology etc. Winding short-circuit fault inspection methods (1) the external inspection make motor no-load running about 20 min, survey winding for the smoke (Short circuit when the number of turns rarely, don't smoke), and then quickly remove the motor, to detect the hot hand winding winding, investigation insulation discoloration, find out the point of failure. (2) with a megger test measure the insulation resistance between the two groups, each if the resistance is very low, to clarify the two interphase short circuit phenomenon. (3) current control method makes the motor no-load running, measurement of three phase current. A phase winding current larger possible fault. Pay attention to three phase power supply voltage, if three-phase voltage imbalance, should adopt swap two phase power tools to check. If the current does not change with the power interchange, is the larger of the phase winding current may have a short circuit fault. Find out after winding short-circuit fault, further find out the point of failure. (4) resistance test use a bridge measurement of each phase winding dc resistance, resistance that may have a smaller phase short circuit fault. But short circuit when the number of turns rarely, it is difficult to measure. (5) short circuit detector test is a short circuit detector on the core around the inductor coil, the bottom surface, so that consistent and stator within weeks of the arc. Detector using the open part on check the stator core notch is checked, the string in the detector coil loop a current meter, and then, the rules of the ac power. This detector coil transformer primary, is the test to become secondary coils. If the coil outstanding, there is no response; If the coil short circuit, that is, current occurs, the current in the primary increase. Investigate the change of the current meter reading, you can find out short circuit fault location. In addition, also can put a small piece of the old metal saw blade in the measured coil another useful edge location notches, if the coil short circuit, was hacksaw will attract and oscillation, a & other; Make & throughout; The sound. When using this method, should pay attention to the following: one is the motor for connection, the delta delta form should be open mouth; Second, winding road is parallel, should open parallel branch; , three is the motor for the double winding by slot being measured has two coils, they lie between a coil pitch separation across at both ends, so to probe (Or metal saw blade)In about two notches are try to determine which is short circuit coil. Treatment method of winding short-circuit fault treatment method is as follows: (1) if the damage is not serious, can be used to repair the turn-to-turn insulation method processing, namely in the damage wrapped insulation tape, coated insulating paint, pad insulation, etc. ; If the loss is serious, should replace winding. (2) the polar group phase short circuit,Short circuit formed by connecting commonly), winding can be heated to 60 ~ 80 ℃, to soften winding insulation, then pry, lead the yellow tube from head to close to the slot, or with good insulating paper pad. Short-circuit point (3) when the short circuit between windings, if in the end, good insulating paper pad. (4) winding interturn short circuit, the current is very big, often several wire coils will burn into a bare wire. At this moment if slot insulation is not completely burned, can be in a few of the short circuit conductor end cut, heating winding, with forceps, extract has a bad wire; If the number of turns of short circuit less than 30% of the total number of turns of groove, is no longer wear new wires, just put the original winding is connected. Of course it will affect the output of the motor. (5) about the high voltage motor, first stripped of insulation repair, cut wire burns part, then a short circuit in conductor of light, it ends file into oblique (The slope length is equal to twice the wire thickness)Staggered, wire turns head indirect necessary. The same scale of conductor, and then matched with silver welding the weld, and bridge measurement of dc resistance welding quality to test. Again according to the original turn-to-turn insulation thickness wound turn insulation, insulating paint coating, drying. Eventually, wrapped the main insulation, such as embedded offline operations.
