If the connection of the
3 phase induction motor is not removed, the star-connected motor can measure the resistance between the phases and the star point. The three-phase resistors must be substantially equal. How to quickly detect the quality of 3 phase induction motors during routine maintenance and installation?
Step 1: Use a vibrating screen to measure the insulation of the ground from a 3 phase induction motor.
For a 380V three-phase motor, a 500V vibrating screen is used. When using a 1000V or 2500V vibrating screen, the electric motor insulation may be destroyed.
Shake the table horizontally and shake the rocker arm at 120rpm to measure the insulation between the electric motor terminals and the electric motor casing. 0.5 megohms or more. Of course, the higher the insulation value, the better, but in reality it is usually tens of megabytes, hundreds of megabytes, or even infinity. If the insulation to ground is too low, you may want to consider repairing electric motor.
In the case of a wound motor, it is also necessary to vibrate the insulation between the stator and the rotor and the insulation between the rotor and the ground.
For the vibration test of high voltage motors, a 2500v vibration meter is generally used. The insulation value should not be lower than 1 mΩ/KV 10 KV motor, and the insulation value to ground is at least 10 megohms.
Step 2: Measure the balance of the three-phase resistance with a multimeter.
If the three phase induction motor connection is not removed, the star-connected motor can measure the resistance between each phase and the star point. The three-phase resistance must be substantially equal. An angled motor can be measured in two-phase to two-phase, and its resistance is substantially equal. If the three-phase resistance of the motor is large and unbalanced, a short circuit between the windings may occur.
Step 3: Also check the mechanical part of the three phase induction motor.
For example, if the bearing is good or bad, after the three phase electric motor is unloaded, manually rotate the disc to ensure that the motor rotates slightly without abnormal noise.
If the above check is not abnormal, you can turn on the motor. After starting up, observe whether the three-phase induction motor runs smoothly and without vibration. Measure whether the current is normal.
More questions are welcome to consult the electric motor manufacturer - Shandong Langrui Industrial Co., Ltd.
