(1) long-term motor over load operation, winding current long-term and excessive, make insulation aging Jiaocui, loss of insulating effect or shaken and crack and fall off.

(2) the winding insulation is affected with damp, without drying, direct access to the power supply, the power supply voltage causes insulation breakdown.

(3) the insulation of the coil group of the stator winding or lead wire is broken or damaged, or when the connection is careless, one or a few coils are short.

(4) for embedded operating line accidentally, electromagnetic line outer layer of insulating material chafed or welding wire, high temperature, touch the end cover, form a short circuit.

(5) because of the assembly operation is not careful, the insulating layer Pengpo electromagnetic wire layer, a short circuit.

(6) in the slot of the winding end or in the slot of the double layer winding, there is no cushion, or the breakdown is damaged.

(7) the end of the winding is too long, touching the end cover, constitute a short circuit.

(8) the electric motor has the elastic pad and the balance pad, which constitute the turn to turn short circuit.