Attention points for maintenance of large and medium-sized motors

Update:07 Dec 2021

We all know that the parts of the machine will wear out after a long time, so we will carry out some maintenance. Taking various motors of different sizes and models commonly used in daily life as an example, introduce what problems should be paid attention to in the maintenance operation.
The motor is generally designed to operate at an altitude of not more than 1000m, and the ambient air temperature does not exceed 40℃. When the additional voltage changes within ±5%, the motor can run continuously at a rated rate. During maintenance of large and medium-sized motors, if the voltage changes more than ±5% When, the load should be limited according to the manufacturer's regulations or test results. The temperature rise of the motor during operation should be in accordance with the manufacturer’s regulations. For the short-term rated motor, the temperature rise limit of each part including the motor commutator is allowed to increase by 10K compared with the specified value. The allowable temperature of the sliding bearing is 80. ℃. The allowable temperature of rolling bearings is 95°C. If the high ambient temperature of the motor is between 40°C and 60°C, the specified temperature rise limit should be subtracted from the value of the ambient temperature exceeding 40°C. When the ambient temperature of the motor is between 0°C and 40°C, the temperature rise limit generally does not increase. After obtaining an agreement with the manufacturer, it is allowed to increase but is as large as 30K. For cage-type asynchronous motors that frequently start at full voltage, special attention should be paid to their heating conditions.
In order to avoid damp, the motor that supplies cooling air from the outside must stop the supply of cooling air in time after the shutdown. Check whether the spark under the brush is normal, and whether the slip ring (or steering gear) is burned and worn. Check whether there is abnormal noise and vibration when the motor is running, and whether the stator and rotor are in friction is also a problem that we need to pay attention to when repairing large and medium-sized motors.

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