In the use of three-phase asynchronous motors, various faults are often generated, such as bearing damage and abnormal winding defects. Therefore, timely and correctly judging the failure of the three-phase asynchronous motor and eliminating it is necessary to ensure the normal operation of the project. The common faults of three-phase asynchronous motors are generally divided into two major categories: mechanical and electromagnetic. Below, Dalan Motors teaches you how to check and judge the short-circuit of the three-phase asynchronous motor windings.
(1) Eye observation method:
Remove the bearing from the shaft end of the motor and clean it with diesel or gasoline. Check the ball, the inner and outer raceways for scratches, cracks or rust. Then fix the inner ring of the bearing and let it rotate. Under normal circumstances, the balance should be rotated, the rotation speed is uniform, the gap is small, there is no noise and it stops slowly. If the noise, vibration, and twisting can be stopped suddenly, the impact sound is generated when the bearing is pushed by hand, or the hand gap is too large, indicating that the bearing is not normal.
(2) Temperature inspection method:
Run for 20 minutes at no load (should stop immediately when an abnormality is found), and touch the motor casing part to exceed the normal temperature by hand.
(3) Power-on experiment method:
Use an ammeter to measure if a phase current is too large, indicating that there is a short circuit in the phase.
(4) Bridge inspection:
Measure the DC resistance of a winding, generally the phase difference should not exceed 5%. If it exceeds, the phase with a small resistance has a short circuit fault.
(5) Short-circuit reconnaissance method:
If the winding to be tested is short-circuited, the steel sheet will vibrate.
(6) Multimeter or megohm method:
Measure the insulation resistance between any two phase windings. If the reading is very small or zero, it indicates that there is a short circuit between the two phases.
(7) Voltage drop method:
The three windings are connected in series and then connected to a low-voltage safety alternating current to measure the voltage drop of each phase winding. A group with a small reading has a short-circuit fault.
(8) Current method:
When the motor runs at no load, the three-phase current is measured first, and the two-phase measurement is exchanged and compared. If it is not changed with the power supply, the one-phase winding of the larger current has a short circuit.
(9) Listen through the ear:
This method is to make the motor run after power-on, and carefully listen to the bearing parts for "click" sound. If the sound is unclear and cannot be placed, use one end of the screwdriver or metal rod to tighten the bearing part, and the other end to listen to the ear. If there is abnormal noise, the bearing wear may be damaged.
The above methods should be used comprehensively to see the nature through the phenomenon, find out the cause of the failure and analyze it, and adopt practical technical measures to solve the substantive problem.
----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant
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