How to measure a three-phase motor good or bad in the easiest way
First summarize how to determine the three-phase asynchronous motor coil good or bad, and what instrument to check:
1. Multimeter: used to check the motor coil on and off measurement.
2. Single-arm bridge: precise measurement of coil resistance, you can know whether the resistance of each phase coil is close.
3. Megameter: used to measure the insulation resistance of the motor between phases and between phases to ground, not less than 0.5 megohm. With 500V megohmmeter insulation resistance is greater than 0.5M that is good, less than 0.5M that the motor is bad, but this is only the appearance of judgment, for the turn-phase breakdown of the short circuit only to dismantle the dismantling of the body check.
There are two main areas of motor failure:
mechanical and electrical
Electrical
1. Whether the three-phase DC resistance is qualified, measured with a double-arm bridge.
2. Insulation resistance is qualified.
Mechanical
1. Whether the end cover “run jacket”, bearing whether “run inner sleeve”.
2. Whether the bearing is lack of oil or damaged.
How to test the motor is good or bad?
1. Shaking table: 500V shaking table can be, shaking the three terminals on the line on the motor shell insulation resistance, should be in 0.5M ohms or more that there is no short circuit to ground.
2. Multimeter measurement: measurement A, B, C three-phase resistance is equal, the larger the motor, the smaller the resistance. But not all three phases are 0 ohms, unless it is a particularly large motor.
3. Check the bearings, fans, general winding motor on all change, sometimes bearing hold dead will also burn the motor.
4. The motor no-load current is generally 10% to 50% of the rated current, sometimes the motor no-load current is still zero.
5. Motor rated current operation, is full load operation, the output power is basically 100%. Running current is small, indicating that the motor output power becomes smaller, is a light load operation.
How to judge the DC motor?
First check if there are broken wires and if the resistance is normal. If it is a brushed DC motor, you can let the rotor rotate, and use a multimeter to measure whether the output DC is normal. If it is a brushless DC motor, and three-phase lead, the rotor can be rotated, with a multimeter to measure the output AC voltage is normal, the output voltage size and speed is proportional.
How to test the AC single-phase motor good or bad?
1. With 500V megohm meter to measure the motor winding and shell insulation resistance should not be less than 0.5 megohm; with a multimeter to measure the winding leads, no broken wire. All of the above meet the requirements, motor performance is good.
2. Detect the capacitor good or bad with a pointer multimeter or digital meter with capacitance file, can be measured directly.
3. The multimeter dial to 1k or 10k resistance gear, measure the capacitor’s 2 leads, the needle quickly deflected to the right slowly back to the left side of the capacitor is good; always to the right side of the description of the capacitor is broken; the pointer does not move the capacitor inside the broken line or no capacity.
How to determine the offline motor good or bad?
1. With a multimeter to measure the DC resistance of the motor three-phase winding, three measurements of the results of the closer the better, the difference of 10% or more, the resistance of a small phase may have occurred turn-to-turn short circuit.
2. With 500V insulation rocking meter to measure the three-phase winding phase insulation resistance and insulation resistance to ground (on the chassis), long-term storage of the motor insulation resistance of 0.5 megohms or more for a good motor, can be used. 0.1 megohms or less than 0.5 megohms indicates that the motor is already damp, to be dried out before use. Insulation resistance is very low that the insulation has been damaged.
