1. Use a multimeter to measure the DC resistance of the three-phase winding of the motor. The closer the result of the three measurements is, the better the winding resistance is within 2%. When the difference is more than 10%, a short-circuit may occur in one phase with small resistance.
2. Use 500v insulation shaker to measure the phase insulation resistance of the three-phase winding and the insulation resistance to the ground (to the casing). The insulation resistance of the motor for long-term storage should be 0.5 megaohm or more as a good motor, which can be used. 0.1 megaohms or more and less than 0.5 megaohms indicates that the motor has been wetted and can be used after drying. A low insulation resistance indicates that the insulation has been damaged.
3. Rotating the rotor of the motor should be easy and free, and there is no noise or friction, indicating that the bearing and air gap are normal.
1. Resistance to ground (high-end position with ohm file): The insulation resistance between the motor winding (three-phase) and the outer casing is generally required to reach 2M or more. In humid, acid-base and other environments, the requirements can be reduced as appropriate. Generally not less than 0.5M.
2, phase resistance (high-end position with ohm file): insulation resistance between different phase windings, generally required to reach 2M or more, in humid, acid and alkali environment can be used to reduce the requirements, generally not less than 0.5M.
3, three-phase resistance (low gear with ohm file): the resistance of the three-phase winding itself, the resistance of the three-phase winding is required to be roughly balanced (accurate data can be obtained by digital meter measurement, motor capacity is different, generally The requirement is no more than 2%).
Third, how to detect the quality of the motor?1. Shake the table and shake the table with 500V. Shake the insulation resistance of the wire on the three terminals to the motor casing. It should be 0.5M or more, indicating that there is no short circuit to the ground.
2, multimeter test: measure the resistance of A / B / C three-phase, whether it is equal, should be similar, too much difference can also turn, but not long, remember that the larger the motor, the smaller the resistance! But not all three phases are 0 ohms, unless you are particularly large, such as motors above 50 kW! Remember that if the speed limit of the 6 terminals of the speed control motor is different!
3, check the bearings, fans, the general wrapped around the motor will be 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. Sometimes the motor idle current is still zero!
5. When the rated current of the motor is running, it is running at full load, and the output power is basically 100%. The running current is small, indicating that the motor output power is small and it is light load operation.
6, no three-phase electricity, find a washing machine's starting capacitor, connect 220V can also turn!
Fourth, how to detect the quality of single-phase motors?Use 500V megger to measure the insulation resistance of the motor winding and the outer casing, which should not be less than 0.5 megohm; use a multimeter to measure the winding leads, no broken wire; the above all meet the requirements, the motor is good.
It is convenient to use the pointer multimeter to detect the quality of the capacitor (there is also a digital meter with a capacitor file, which can be directly measured).
Turn the multimeter to the 1K or 10K resistor, measure the two leads of the capacitor, and the pointer is quickly deflected to the right and slowly return to the left capacitor. The capacitor is always deflected to the right; the capacitor is not moved. Internal disconnection or no capacity. In this way, only the quality of the capacitor can be judged, and the size of the capacity needs to be estimated by long-term experience.
5. How to detect the quality of the ventilation fan motor?There is a multimeter. You can measure the three ends of the motor with the multimeter's resistance file (X10). It should be interoperable, but the resistance is not the same. Red (fire line) and black (zero line) + blue (connected capacitor) And black (zero line) = red and blue black resistance is greater than red and black resistance, generally it is possible that red and blue are open (with resistance), and black and red, blue are not connected, that is, the inside of the motor The overheat protection is burned out. If there is a replacement, it will be replaced. If you don't have it, you can skip it. You can skip it.
Sixth, how to detect the quality of lathe two-speed motor?1) The three-phase resistance value (measured U1, V1, W1) when measuring the angle is the same as the three-phase resistance.
2) The three-phase resistance value when measuring double stars (measuring U2, V2, W2, U1, V1, W1 shorted) should be the same as the three-phase resistance.
3) The insulation resistance of the motor winding to ground should be greater than 5 megohms.
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