1. How to check the quality of AC three-phase motor?

1. Shake the watch, a 500V watch can be shaken, and the insulation resistance of the wires on the three terminals to the motor casing should be above 0.5M ohms, indicating that there is no short circuit to ground.

2. Multimeter test: measure the resistance between the three phases of A/B/C, whether they are equal, it should be about the same, and the difference can be turned too much, but it will not be used for long, remember that the larger the motor, the smaller the resistance! But Can't all three phases be 0 ohms, unless you are a very large motor, such as a motor above 50KW! Remember that if it is a speed-regulated motor, the resistance of the 6 terminals is different!

3. Check the bearings and fans. Generally, the motor will be completely replaced! Because sometimes the bearing locks will burn the motor!

4. The no-load current of the motor is generally 10% to 50% of the rated current, and sometimes the idling current of the motor is zero!

5. When the motor is running at rated current, it is running at full load. The running current is small, indicating that the output power of the motor becomes smaller, and it is light-load operation.

2. How to detect the quality of AC single-phase motor?

Use a 500V megohmmeter to measure the insulation resistance of the motor windings and the casing, which should not be less than 0.5 megohms. Use a multimeter to measure the leads of the windings. If there is no disconnection, the above requirements are met, and the motor is good. It is more convenient to use a pointer multimeter to detect the quality of the capacitor (there is also a digital meter with a capacitance gear, which can be directly measured). Turn the multimeter to the 1K or 10K resistance gear, measure the 2 leads of the capacitor, and the needle quickly deflects to the right and then slowly returns to The capacitor on the left is good, and the right side shows that the capacitor is broken down. If the pointer does not move, the internal wire of the capacitor is broken or there is no capacity. This method can only judge the quality of the capacitor.

3. Is the DC motor good or bad?

First see if there is any disconnection, and test whether the resistance is normal. If it is a brushed DC motor, you can let the rotor rotate and use a multimeter to test whether the output DC is normal. If it is a brushless DC motor with three-phase leads, the rotor can be rotated, and a multimeter can be used to test whether the output AC voltage is normal. The output voltage is proportional to the rotational speed.