Three-phase AC motors are extremely convenient to use and have gained widespread recognition due to their inherent advantages. However, after prolonged operation, faults may occur in the motor, adversely affecting its application. How does Xianyang SIMO Motor handle three-phase AC motor faults? How do we address such issues?SIMO Motorhas compiled the relevant materials. Let’s take a look.

The winding is a component of the three-phase AC motor. Aging, moisture, high temperature, corrosion, foreign object intrusion, and external mechanical impact can all damage the winding. Motor overload, undervoltage, and overvoltage can also lead to winding faults. Winding faults are generally categorized as ground faults, short circuits, open circuits, and wiring faults. Below, the fault phenomena, causes, and inspection methods are explained separately.

　　1. Fault Phenomena

The three-phase AC motor fails to operate normally due to energized housing, loss of control over control wiring, short circuits, and winding overheating.

　　2. Causes

Reduced winding insulation resistance; prolonged motor overload operation; corrosive gases; metallic foreign objects intruding into the winding interior and damaging insulation; insulation damage caused by collision with the stator core during rewinding of stator windings; winding ends contacting the end shield or frame; friction between stator and rotor causing insulation burnout; insulation damage on lead wires resulting in contact with the housing. Overvoltage (e.g., lightning strikes) may cause insulation breakdown.

　　3. Inspection Methods

(1) Visual Inspection. Inspect the winding ends and slot insulation visually for signs of damage or discoloration (e.g., blackening); if present, locate the affected connection point.

(2) Multimeter Method. A very low reading indicates a ground fault.

(3) Megohmmeter Method. Select an appropriate megohmmeter based on the motor’s voltage class to measure the insulation resistance of each winding group. A reading of zero indicates a ground fault. However, for motors whose insulation has been compromised by moisture or accident, judgment must rely on experience: typically, irregular pointer oscillation near “0” suggests a certain residual resistance value.

(4) Test Lamp Method. If the test lamp illuminates, a ground fault exists. Sparks or smoke at a specific location indicate the ground fault point. A dimly lit lamp suggests a partial ground fault due to degraded insulation. If the lamp remains unlit but sparks appear when the test probe contacts ground, the winding is not fully shorted but severely damp. Alternatively, strike the housing’s stop edge gently with a hardwood block; if the lamp extinguishes and reignites upon impact at a particular spot, that location corresponds to the ground fault point—current interruption and reconnection occurs there.

(5) Current-Induced Burn Method. Using a variable-voltage transformer, apply power; the fault location will rapidly heat up, and smoke emerging from the insulation identifies the ground fault point. Special caution is required: for small motors, current must not exceed twice the rated current for more than 30 seconds; for large motors, current should be limited to 20–50% of rated current—or gradually increased—cutting off power immediately once smoke appears at the ground fault location.