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What are the causes of motor bearing damage?

What are the causes of motor bearing damage?

2023-01-14

Motor burnout Phenomenon: Under normal circumstances, the motor burned out by overload is completely black in the winding coil; the motor burned out by lack of phase is divided into two types: delta connection and star connection. The phase windings are burnt black; the star-connected motor is burned black with two-phase windings; the rest are caused by inter-turn short circuit, insulation damage, water ingress or foreign object damage.


The direct cause of motor burnout is high temperature. The main reasons for the high temperature of the motor:


1. Reasons inside the motor itself: (1) Phase-to-phase and inter-turn short-circuit or grounding of the windings, resulting in increased winding current, unbalanced three-phase current, and overheating of the motor. (2) When the motor is running, the three-phase current is seriously unbalanced, generating noise and vibration, and the motor is overheated. (3) The stator and rotor generate frictional heat. (4) The cage rotor guide bar of the asynchronous motor is broken, or the wound rotor winding is broken. Insufficient motor output and overheating. (4) The motor bearing is completely damaged and cannot rotate, and the motor shaft is locked and locked. (5) If it is damp, the winding insulation will be reduced. (6) End of useful life. After the insulation is aged, there may be problems such as short circuit between phases, short circuit between smashes, and breakdown to ground, which may cause the motor to burn out inadvertently.


2. Reasons for the load of the motor: (1) The motor runs under overload for a long time. (2) The motor starts frequently, the starting time is too long or the starting interval is too short. (3) The dragged mechanical failure increases the output of the motor, or it is stuck and does not rotate or the speed drops sharply, causing the motor current to increase sharply and overheat. (4) The working system of the motor does not match the load working system. For example, the motor of the short-term cycle working system is used to drive the load that works continuously for a long time.


3. Reasons for the environment and ventilation and heat dissipation: (1) The working environment and ventilation of the motor are poor, and the motor cannot get good ventilation and heat dissipation and overheats. (2) Too much dust and grease in the motor will affect the heat dissipation of the motor. (3) The windshield or the windshield inside the motor is not installed, resulting in poor air flow and poor heat dissipation of the motor. (4) The fan is damaged, deformed, loose, or not installed or installed upside down, resulting in poor ventilation and heat dissipation of the motor. (5) There are too many defects in the heat dissipation ribs of the enclosed motor shell, and the heat dissipation area is reduced; or the fan of the protective motor is blocked. (6) Voltage instability is too high or too low. (7) The power supply phase is missing.

There are other reasons that are not very common, such as: the voltage is too low or too high, the vibration causes the terminal to be loose and short-circuited between phases, pests and mice, and the voltage of imported motors does not match the domestic voltage (such as Japanese motors). Various decompression starting circuit failures cause no switching, long-term low-voltage operation of the motor, etc.


The maintenance method of motor burnout: replace the winding coil of the motor, soak it in insulating varnish and dry it; replace the custom bearing; repair the rotor core.


The motor is soaked in water and damp


Water or damp in the motor will cause the insulation performance to decrease, which is also a common cause of damage. Before it is burned, the power should be cut off in time, and the motor should be dried and re-dipped in paint. Especially for motors driven by frequency converters, you must be more careful about this, otherwise the frequency converter may be burned.


If the motor has been soaked in water, check the wholesale bearings and replace them if necessary.


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