Three-phase asynchronous motor winding short circuit

Due to the large motor current is too large and the change of supply voltage mini electric motor and single phase operation,mechanical,manufacturing bruised bad insulation damage caused by such as winding interturn short circuit,short circuit between windings,winding interelectrode interphase short circuit and winding short circuit.Fault phenomenon: 1.The magnetic field distribution of ions,three phase current balance and make the motor vibration and noise when running,serious acmotortrading.blogspot.com when motor can't start,and have great short-circuit current in coil of short circuit,lead to rapid heating coil and burned.2.The reason: motor overload for a long time,lose insulation aging of insulation;Wire insulation damage;Winding be affected with damp be affected with damp decreased insulation resistance caused by insulation breakdown;End and not cushion layer insulation material or plastic damage;End connection wire insulation damage;Or been struck by lightning overvoltage insulation breakdown;Friction between rotor and stator winding end insulation damage;Too many metal foreign bodies fall into the inside of the motor and oil pollution.

3.Check: (1) the external observation method.Observation of junction box,winding end with or without burning,winding overheating after leave a dark brown,and has a bad smell.(2) temperature control method.No-load running for 20 minutes (found abnormal should immediately stop),with the back of hand touch winding parts ac electric motors is more than normal temperature.(3) the electricity experiment method.With current meter measurement,if one phase current is too large,have indicated that the phase short circuit.(4) the bridge inspection.Measuring a winding dc resistance,general difference should not exceed 5%,such as more than small,resistance of a phase short circuit fault.(5) short circuit detection method.There is a short circuit the winding under test,the sheet steel can produce vibration.(6) multimeter or megohmmeter.And any two phase winding insulation resistance measurement,if read very small or zero,shows that the two phase winding and has a short circuit.(7) voltage drop.After the three winding in series into the low voltage security alternating current (ac),the study measured a group of small fault.(8) current method.Motor no-load running,to measure the three phase current,in two phase switch,measure and electric motors price contrast,if he does not change with the power switch,a phase winding large current has the short circuit.

4.Short circuit processing method: (1) the short circuit point in the end.Insulating materials available to separate short-circuit point,also can be double insulated wire,to paint drying.(2) short circuit online slot.After the softening,find out the short circuit point repair,back into the trough,then paint drying.(3) the short route turns less than 1/12 of each phase winding,the serial number of turns all cut short route,connect the conduction part,forming a closed loop,supply urgent use.(4) winding short-circuit point when the number of turns more than 1/12,to dismantle all rewind.