Causes of Winding Short Circuit in Asynchronous Motors

Causes of Winding Short Circuit in Asynchronous Motors

(1) The motor runs under overload or overvoltage for a long time, causing the current in the winding to be too large and heat up, which accelerates the aging of the insulation, making the insulation brittle and cracking, and losing its insulating function, or the brittle insulation falls off due to vibration during operation.

(2) When repairing an electric motor, the outer insulation of the enameled wire is damaged due to careless operation, or the insulation at the welding point is aged or damaged due to excessively high temperature or too long welding time.

(3) The motor that has been out of service for a long time has its insulation damp and is put into operation without insulation drying. The damp insulation is broken down and causes a short circuit.

(4) The slots of the double-layer winding are damaged due to breakdown due to poor insulation between phases.

(5) The phase-to-phase insulation at the end of the single-layer winding is not properly padded or slips during the end binding, causing the phase-to-phase insulation at the end to break down and cause a short circuit.

(6) The winding end is too long, touching the end cover or the insulation is not properly padded.

(7) The burrs at the joints of the pole-phase group connecting wires and the lead-out wires at the winding ends were not properly handled after welding, causing the burrs to pierce the insulation and cause a short circuit.

(8) Short circuits are caused by poor insulation or too low insulation strength of the connecting wires or lead wires between the coil groups of the stator winding.

(9) The winding wiring is incorrect, causing one or several coil groups to short-circuit.

(10) When cleaning the motor site, water is used to flush the motor, causing water to enter the motor and cause a short circuit.

Causes of stator winding short circuit in three-phase asynchronous motor

Stator winding short circuit is a common fault in three-phase asynchronous motors. Winding short circuit can be divided into turn-to-turn short circuit and phase-to-phase short circuit, among which phase-to-phase short circuit includes short circuit between adjacent coils, short circuit between pole-phase groups and short circuit between two-phase windings; turn-to-turn short circuit refers to the short circuit of two turns in series in the coil due to insulation rupture. Phase-to-phase short circuit refers to the short circuit caused by insulation damage between adjacent coils, short circuit of two leads of a pole-phase group, and short circuit between two phases of three-phase winding due to insulation damage.

When the winding is seriously short-circuited, the motor cannot start at all under load. If the number of short-circuited turns is small, the motor can start, but the current is large and the three-phase is unbalanced, resulting in unbalanced electromagnetic torque, causing the motor to vibrate and emit a "buzzing" sound. A large current flows through the short-circuited turns, causing the winding to heat up quickly, smoke, emit a burnt smell, or even burn out.

1. The wire embedding operation is not skilled during repair, resulting in insulation damage, or the temperature of the soldering iron is too high and the welding time is too long when welding the lead, which burns the insulation of the coil.

2. The insulation of the winding has aged due to disrepair, or the winding has become damp and is operated directly without drying, resulting in insulation breakdown.

3. The motor is overloaded for a long time, and the current in the winding is too large, causing the insulation to age, the insulation performance to decrease and lose its insulation function.

4. The insulation of the connecting wires or leads between the stator winding coils is poor.

5. When the winding is rewound, the phase insulation at the winding end or in the double-layer winding slot is not well padded or is damaged by breakdown.

6. Due to severe bearing wear, the friction between the stator and rotor cores generates high heat, causing the stator winding insulation to burn out.

7. Lightning strike, too many consecutive starts or overvoltage breakdown of insulation.