(1) The motor is overloaded. Such as: friction between stator and rotor (commonly known as sweeping), unqualified assembly, and overload faults such as friction or jamming in the driven mechanical parts.

(2) The motor runs without phase.

(3) The unbalance degree of three-phase voltage and three-phase current exceeds the specified allowable range.

(4) The power supply voltage is too high or too low, which exceeds the allowable variation range of the rated voltage of the motor (ie ±10%).

(5) The wiring of the motor winding is wrong. For example: a certain phase end of the stator winding is connected reversely.

(6) There is a fault in the motor winding. Such as: short circuit between winding turns or layers, winding grounding.

(7) The insulation between the stator iron core silicon steel sheets is damaged, so that the stator iron core is short-circuited, causing the eddy current of the stator iron core to increase, causing the motor to overheat.

(8) Frequent startup.

(9) The motor air duct is blocked and the ventilation is poor.

(10) The ambient temperature around the motor is too high (exceeding the +40°C specified in the design), resulting in poor heat dissipation and poor cooling effect.

Due to the difference between the use place of the motor and the ambient temperature, the "temperature rise" is often used to indicate the strength of the actual heat resistance of the motor insulation material. The so-called temperature rise refers to the temperature of electrical equipment (including electric motors) higher than that of the environment. The rated temperature rise of the motor refers to the allowable temperature rise of the motor winding under the ambient temperature (+40°C) specified in the design, which depends on the insulation grade of the winding. The insulation grade of a motor is a grade that indicates that the insulating material used in the motor winding can withstand the temperature limit.