Maintenance methods for motors

    There are two main types of motor faults: mechanical faults and electrical faults. Mechanical faults are relatively easy to detect, while electrical faults need to be analyzed and judged by measuring their voltage or current. The following are common methods for detecting and troubleshooting motor faults.

   1. The no-load current of the motor is high
    When the no-load current of the motor exceeds the limit data, it indicates that the motor has malfunctioned. The reasons for the high no-load current of the motor include high mechanical friction inside the motor, local short circuit in the coil, and demagnetization of the magnetic steel. We will continue with the relevant testing and inspection items to further determine the cause or location of the malfunction.
    If the no-load/load speed ratio of the motor is greater than 1.5, turn on the power and rotate the handle to make the motor rotate at high speed without load for more than 10 seconds. After the motor speed stabilizes, measure the maximum no-load speed N1 of the motor at this time. Under standard test conditions, drive a distance of more than 200m and start measuring 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 indicates that the demagnetization of the motor's magnetic steel has been quite severe. The entire set of magnetic steel inside the motor should be replaced. In the actual maintenance process of electric vehicles, the entire motor is usually replaced.

   2. Motor heating
    The direct cause of motor heating is due to high current. The relationship between the motor current I, the input electromotive force E1 of the motor, the induced electromotive force (also known as back electromotive force) E2 of the motor rotation, and the resistance R of the motor coil is: I=(E1-E2) ÷ R. An increase in I indicates a decrease in R or a decrease in E2. A decrease in R is usually caused by a short circuit or open circuit in the coil, while a decrease in E2 is usually caused by demagnetization of the magnetic steel or a short circuit or open circuit in the coil. In the maintenance practice of electric vehicles, the method to deal with motor overheating and fault discharge is generally to replace the motor.

   3. There is mechanical collision or noise inside the motor during operation
    Both high-speed and low-speed motors should not experience mechanical collisions or discontinuous and irregular mechanical noise during load operation. Different forms of motors can be repaired using different methods.
   4. Shortened driving range and weak motor
    The reasons for short driving range and weak motor (commonly known as weak motor) are quite complex. But after ruling out the above four types of motor faults, generally speaking, faults with short driving range of the whole vehicle are not caused by the motor. This is related to the attenuation of battery capacity, insufficient charging of the charger, and controller parameter drift (PWM signal not reaching 100%).
   5. Brushless motor phase loss
    The lack of phase in brushless motors is generally caused by damage to the Hall components of the motor. We can use the comparison method to determine which Hall element is faulty by measuring the resistance of the output lead of the Hall element relative to the Hall ground wire and the lead relative to the Hall power supply.
    To ensure the accuracy of the motor commutation position, it is generally recommended to replace all three Hall components simultaneously. Before replacing the Hall components, it is necessary to determine whether the phase angle of the motor is 120 ° or 60 °. Generally, the placement of the three Hall components in a 120 ° phase angle motor is parallel. And for a 60 ° phase angle motor, one of the three Hall elements is placed in a flipped 180 ° position.