Technician's troubleshooting method for motor heating fault

When the temperature of the motor exceeds the maximum operating temperature or the temperature rise exceeds the specified value, or when the temperature rise suddenly increases at low load although it does not exceed the specified value, it indicates that there is a fault in the motor. The diagnosis and troubleshooting methods are:

(1) Under rated load, the temperature rise did not exceed the temperature rise limit, only due to the ambient temperature exceeding 40 ℃, causing the motor temperature to exceed the maximum allowable operating temperature. This phenomenon indicates that the motor itself is normal. The solution is to manually lower the ambient temperature. If this is not possible, the load must be reduced during operation.

(2) The temperature rise exceeds the nameplate specifications under rated load. Regardless of the situation, it is a fault with the motor and must be stopped for inspection, especially when there is a sudden increase in temperature rise. The external reasons include: low grid voltage or excessive line voltage drop (more than 10%), heavy load (more than 10%), and improper coordination between motors and machinery; Internal reasons include: single-phase operation, turn to turn short circuit, phase to phase short circuit, stator grounding, fan damage or loose fastening, air duct blockage, bearing damage, rotor stator rubbing, motor and cable joint heating (especially copper aluminum or aluminum aluminum connection), motor corrosion or moisture, etc.

(3) In theory, motors can rotate in both forward and reverse directions, but some motors have directional fans (most of which are 2P motors), and if they are reversed, the temperature rise will exceed a lot.