Inter-turn short circuit is one of the more common faults of three-phase asynchronous motors, and the causes of the fault are also various. Today, the editor of Dalan Motor combined with the actual case and found an exchange with everyone.

1. Causes and hazards of interturn faults

(1) The contact area between the turns of the motor winding is basically the same as the turn length of the winding. Inter-turn insulation is often the insulation of the electromagnetic wire itself or very thin additional inter-turn insulation, such as films or mica pads. The dielectric strength of the turn-to-turn insulation is far inferior to the insulation to ground.

(2) The winding insulation of the motor is subjected to power frequency voltage, instantaneous overvoltage, operating overvoltage and lightning overvoltage during operation. These voltages act on both ground insulation and turn-to-turn insulation. The main factors that damage the turn-to-turn insulation are various overvoltages.

(3) The short-circuit turn of the inter-turn fault is generated inside the motor. Under the action of the alternating magnetic field, the induced electromotive force is generated. The short-circuit turn forms a loop. Over time, the insulation material will age and become brittle and fall off, starting from damage to the insulation , May cause the motor to burn out.

2. Handling of inter-turn faults

(1) For the low-voltage loose embedded winding, during the winding and embedding process, carefully check the quality of the wire and observe whether the color of the insulating layer of the paint film is uniform, whether there are scratches, bubbles, etc. If necessary, use a film or scotch tape to cover it.

(2) If the fault point cannot be found or handled in the groove and at the end according to the above method, the faulty wire can be pulled out of the groove, the wire can be replaced or rerouted, and then embedded into it, avoiding the turn The weak point makes the winding turn-to-turn withstand voltage meet the standard requirements.

3. Key points of turn-to-turn fault control

(1) The quality of the electromagnetic wire itself. Control the quality of the electromagnetic wires through the necessary detection indicators, especially the key points are room temperature withstand voltage, twisting peeling and paint film continuity.

(2) Winding link control. In the winding process, on the one hand, it is necessary to ensure the compliance of the winding mold, and it cannot damage the electromagnetic wire from thousands of factories. On the other hand, the drag of the electromagnetic wire and the direct friction between the electromagnetic wire and the spool edge cause damage to the paint.

(3) In the process of wire embedding, the electromagnetic wire and the notch, the scribe board is not smooth, the pressure plate is strongly pressurized, the cutting tool is too sharp, and the end is shaped, etc. may cause partial damage to the electromagnetic wire.

(4) The non-conformance of the binding tool during the wiring process and the non-conformity of the spreader during lifting will cause partial damage to the winding.

(5) Undesirable factors such as the bouncing of the core slot, uneven bottom of the slot, and iron filings in the slot will cause damage to the electromagnetic wire to varying degrees, resulting in turn-to-turn.

(6) The stator is damp, especially the infiltration of corrosive substances, which can cause partial damage to the motor and seriously damage the winding of the entire motor.

(7) In the drying process, excessively high furnace temperature leads to impaired insulation performance.

----- Responsible Editor: Dalan Oil Pump Motor 02-Procurement Consultant

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