The fault detection and elimination method of the motor, generally divided into the following points

1, the motor no-load current is large

Measurement methods are as follows: use the multimeter 20A gear, the multimeter red and black meter in series with the power input of the controller. Turn on the power supply, in the case of the motor does not rotate, record the current value of the multimeter A1, turn the handle, so that the motor high-speed no-load rotation for more than 10 seconds, after the motor speed stability, start to observe and record the value of the multimeter A2. motor no-load current = A2 - A1.

The reference table of no-load current of various motors without fault is as follows.

Motor form rated voltage 24V rated voltage 36V

Side hung motor 2.2A 1.8A

High-speed brushed motor 1.7A1.0A

Low-speed brush motor 1.0A0.6A

High-speed brushless motor1.7A1.0A

Low-speed brushless motor 1.0A0.6A

When the no-load current of the motor is greater than the reference table limit data, it indicates that the motor is malfunctioning. The reasons for high no-load current of the motor are: 1) large mechanical friction inside the motor. 2) local short circuit of the coil. 3) demagnetization of the magnets. We continue down to do the relevant tests and check items, you can further determine the cause of the fault or fault parts.

2, the motor no-load / load speed ratio greater than 1.5

Measurement methods are as follows: turn on the power, turn the handle, so that the motor high-speed no-load rotation for more than 10 seconds, after the motor speed stability, with a handheld speed / speed measurement meter to measure the motor no-load speed N1, under the standard load, travel more than 200m distance, start measuring the motor load speed N2.

No-load/load speed ratio = N2÷N1

When the no-load/load speed ratio of the motor is greater than 1.5, it means that the magnet demagnetization of the motor has been quite powerful, should replace the whole set of magnets inside the motor, generally in the actual maintenance process of electric vehicles is to replace the whole motor.

3、Motor heating

With non-contact infrared thermometer, or multimeter temperature measurement gear (with temperature measurement multimeter), measuring the temperature of the motor end cover more than 30 ℃ above the ambient temperature, indicating that the temperature rise of the motor has exceeded the normal range, the general temperature rise of the motor in the following 25 ℃.

The direct cause of motor heating is caused by high current. The relationship between the motor current i, the input electric potential E1 of the motor, the inductive electric potential (also called counter-electric potential) E2 of the motor rotation, and the motor coil resistance R is

i = (E1 - E2) ÷ R

R is generally caused by a short circuit or open circuit in the coil, and E2 is generally caused by demagnetization of the magnet or a short circuit or open circuit in the coil.

In the electric vehicle maintenance practice, the motor fever fault, generally is to replace the motor.

4, the motor in the operation of the internal mechanical collision or mechanical noise.

Whether high-speed motor or low-speed motor, there should be no mechanical collision or discontinuous irregular mechanical noise when the load is running.

5, brushless motor is out of phase

Brushless motor phase loss is generally caused by damage to the brushless motor's Hall element, we can measure the resistance of the Hall element output lead relative to the Hall ground and relative to the Hall power lead, using the comparison method to determine which Hall element is faulty.

In order to ensure the accuracy of the motor phase change position, it is generally recommended to replace all three lug elements at the same time. Before replacing the lug element, it must be clear whether the phase algebraic angle of the motor is 120 degrees or 60 degrees, generally the placement of the three lug elements of a 60 degree phase angle motor is parallel. While the 120 degree phase angle motor, the middle of the three lug elements of a lug element is flip 180 degrees position placement.