Daily Maintenance and Inspection of Three-Phase Asynchronous Motors
Date：2023-10-07
GUANGZHOU HAOQING MOTOR CO.,LTD
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Proper inspection of electric motors is highly beneficial to extending their service life. A three-phase asynchronous motor is an induction motor. When current is supplied to the stator, part of the magnetic flux passes through the short-circuit rings and induces currents in them. The three-phase winding consists of three independent windings, each of which is formed by connecting several coils. Each winding represents one phase, and the three windings are spatially displaced by 120 electrical degrees from one another. Coils are wound with insulated copper or aluminum conductors. Small and medium-sized three-phase motors mostly use round enameled wires, while the stator coils of large and medium-sized three-phase motors are wound with insulated rectangular copper or aluminum wires of larger cross-section, and then inserted into the slots of the stator core in a specified pattern.
Three-phase asynchronous motors tend to deteriorate as their service years increase, so it is necessary to strengthen their daily maintenance. Here, we share how to enhance the daily inspection of such motors.
Inspection of Voltage and Current
1. Check whether the power supply for the three-phase asynchronous motor meets the requirements. If the voltage fluctuation exceeds +10% and -5% of the rated value, the power supply conditions shall be improved.
2. Check the current balance under the condition of balanced voltage, and the motor shall not operate in an overloaded state (i.e., exceeding the rated value) for a long time.
3. Inspect the auxiliary starting and protection devices of the motor to ensure they are in good condition.
4. Check whether the ratio of the no-load current to the rated current is normal.
Inspection of Bearings
Bearing conditions are inspected by monitoring for abnormal noise of the three-phase asynchronous motor, measuring vibration, and taking bearing temperature readings. Special attention shall be paid when the calculated rated service life of the bearing is approaching. Check the bearing temperature (the upper limit temperature for rolling bearings is 90°C).
Bearing Replacement
New bearings shall be thoroughly cleaned with gasoline or alcohol. The bearings can be heated to 120°C using methods such as an oven or induction heating, then fitted onto the bearing seat of the rotating shaft, and allowed to cool naturally to room temperature.
Inspection of Shaft Seals and Installation
Inspect the condition of the shaft seals of the three-phase asynchronous motor and replace the seals if necessary. Check the condition of connecting parts, as well as mounting and assembly bolts.
Inspection of Wiring
1. Ensure the wiring configuration (delta, star) is correct.
2. Verify that the casing of the three-phase asynchronous motor is properly and firmly grounded.
