Detection And Elimination Of Common Faults Of Motor

1. The no-load current of the motor is large

When the no-load current of the motor is greater than the limit data, it indicates that the motor has a fault. The reason for the high no-load current of the motor is that the internal mechanical friction of the motor is large, the coil is partially short-circuited, and the magnetic steel is demagnetized. We can further determine the cause or location of the fault by continuing to do the relevant test and inspection items.

If the no-load/load speed ratio of the motor is greater than 1.5, turn on the power supply and turn the knob to make the motor rotate at high speed and no-load for more than 10s. After the motor speed is stable, measure the maximum no-load speed N1 of the motor at this time. Under standard test conditions, drive more than 200m and start to measure the maximum load speed N2 of the motor. No-load/load ratio=N2 ÷ N1.

When the no-load/load speed ratio of the motor is greater than 1.5, it means that the magnetic steel of the motor has been demagnetized quite severely. The complete set of magnetic steel in the motor should be replaced. In the actual maintenance process of electric vehicles, the whole motor is usually replaced.

2. Motor heating

The direct cause of motor heating is due to high current. The relationship between motor current I, motor input electromotive force E1, motor rotation induced electromotive force (also called back electromotive force) E2, and motor coil resistance R is: I=(E1-E2) ÷ R, I increases, indicating that R decreases or E2 decreases. The decrease of R is generally caused by coil short circuit or open circuit, and the decrease of E2 is generally caused by demagnetization of magnetic steel or coil short circuit or open circuit. In the maintenance practice of the whole electric vehicle, the method to deal with the heating and blocking of the motor is generally to replace the motor.

3. There is mechanical collision or mechanical noise inside the motor during operation

No matter high-speed motor or low-speed motor, there should be no mechanical collision or discontinuous and irregular mechanical noise during load operation. Different types of motors can be repaired by different methods.

4. Shorten driving mileage and motor fatigue

The reasons for the short driving range and the lack of motor power (commonly known as the lack of motor power) are relatively complex. However, after we have eliminated the above four motor faults, generally speaking, the fault of short driving range of the whole vehicle is not caused by the motor, which is related to the attenuation of battery capacity, insufficient charger charge, controller parameter drift (PWM signal does not reach 100%), etc.

5. Brushless motor phase loss

The phase loss of brushless motor is generally caused by the damage of Hall element of brushless motor. By measuring the resistance of the output lead of the Hall element relative to the Hall ground wire and the lead of the Hall power supply, we can use the comparison method to determine which Hall element is faulty.

To ensure the accuracy of the commutation position of the motor, it is generally recommended to replace all three Hall elements at the same time. Before replacing Hall elements, it must be clear whether the phase algebraic angle of the motor is 120 ° or 60 °. Generally, the three Hall elements of the 120 ° phase angle motor are placed in parallel. For a 60 ° phase angle motor, one Hall element in the middle of the three Hall elements is placed in a 180 ° inverted position.