How to measure the quality of a three-phase motor in the simplest way?-Xinda Motor- electric motors and EV accessories supplier|INDEX--

How to measure the quality of a three-phase motor in the simplest way?

Date：2024-06-11　　　Author：XINDA MOTOR

Editor's Note

There are actually many aspects to judge the quality of an electric motor. Today, the editor has sorted out a few points and hopes that it will be helpful to everyone.

First, let's summarize how to judge the quality of the three-phase asynchronous motor coil and what instrument to use to check:

1. Multimeter: used to check the continuity of motor coils.

2. Single-arm bridge: Accurately measure the coil resistance to know whether the resistance of each phase coil is close.

3. Megaohm meter: used to measure the insulation resistance between phases and between phases and ground of the motor, which should be no less than 0.5 megohms. If the insulation resistance is greater than 0.5M with a 500V megohmmeter, it means it is good, and if it is less than 0.5M, it means the motor is broken. However, this is only an appearance judgment. For turn-to-turn short circuit and phase-to-phase breakdown, it can only be disassembled and inspected.

There are two main reasons for the failure of electric motors: mechanical and electrical.

Electrical

1. Check whether the three-phase DC resistance is qualified by measuring with a double-arm bridge.

2. Whether the insulation resistance is qualified.

Mechanical aspects

1. Check whether the end cover is running off the outer sleeve and the bearing is running off the inner sleeve.

2. Check whether the bearing is short of oil or damaged.

How to detect whether the motor is good or bad?

1. Meter: A 500V megger will do. Meter the insulation resistance of the wires on the three terminals to the motor housing. If it is above 0.5M ohms, it means there is no short circuit to the ground.

2. Use a multimeter to test whether the resistance between phases A, B, and C is equal. The larger the motor, the smaller the resistance. However, all three phases cannot be 0 ohms unless it is a very large motor.

3. Check the bearings and fans. Generally, if the motor is entangled, they should all be replaced. Sometimes the bearings may lock and the motor may burn.

4. The no-load current of the motor is generally 10% to 50% of the rated current. Sometimes the no-load current of the motor is still zero.

5. When the motor is running at rated current, it is running at full load, and the output power is basically 100%. If the running current is small, it means that the motor output power is reduced, and it is running at light load.

How to judge the quality of DC motor?

First check if there is any broken wire and whether 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 the three-phase lead is used, the rotor can rotate, and use a multimeter to measure whether the output AC voltage is normal. The output voltage is proportional to the speed.

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

1. Use a 500V megohmmeter to measure the insulation resistance of the motor winding and the housing, which should not be less than 0.5 megohms; use a multimeter to measure the leads of the winding, and there should be no broken wires. All of the above items meet the requirements and the motor performance is good.

2. To check whether the capacitor is good or bad, use a pointer multimeter or a digital meter with a capacitance range for direct measurement.

3. Set the multimeter to the 1k or 10k resistance range, measure the two leads of the capacitor, and if the needle quickly deflects to the right and then slowly returns to the left, the capacitor is good; if it always deflects to the right, it means the capacitor is broken; if the pointer does not move, the internal wire of the capacitor is broken or there is no capacity.

How to judge whether an offline motor is good or bad?

1. Use a multimeter to measure the DC resistance of the three-phase winding of the motor. The closer the results of the three measurements are, the better. When the difference is more than 10%, the phase with smaller resistance may have a turn-to-turn short circuit.

2. Use a 500V insulation megohmmeter to measure the insulation resistance between the three-phase windings and the insulation resistance to the ground (to the housing). If the insulation resistance of the motor stored for a long time reaches 0.5 megohms or more, it is a good motor and can be used. If it is more than 0.1 megohms but less than 0.5 megohms, it means that the motor has been damp and can be used only after drying. If the insulation resistance is very low, it means that the insulation is damaged.

How to measure the quality of a three-phase motor in the simplest way?

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