A professional motor maintenance process includes cleaning the stator and rotor, replacing carbon brushes or other parts, vacuum pressure impregnation with Class F varnish, drying and dynamic balancing.
1. Keep the operating environment dry, the motor surface clean, and the air inlet free of dust, fibres and other obstructions.
2. If thermal protection repeatedly operates, determine whether the cause is a motor fault, overload or an excessively low protection setting. Correct the fault before returning the motor to operation.
3. Maintain adequate lubrication. The original guide recommends replenishing or replacing grease after around 5,000 operating hours and replacing it promptly if bearings overheat or lubricant deteriorates. Remove old lubricant, clean the bearing and cover grooves with petrol as specified in the original guide, and fill the space between the inner and outer bearing rings with ZL-3 lithium grease: one half for two-pole motors and two thirds for four-, six- and eight-pole motors.
4. At the end of bearing life, vibration and noise increase noticeably. Check radial clearance and replace the bearing when it reaches the specified limit.
5. The rotor can be removed from either the shaft-extension or opposite end. If the fan does not need removal, the opposite end is usually more convenient. Avoid damaging stator windings or insulation when withdrawing the rotor.
6. Before replacing windings, record the original winding type, dimensions, number of turns and wire gauge. If this information is lost, obtain it from the manufacturer. Changing the original winding design without proper specifications can impair performance or make the motor unusable.