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How to measure whether the brushless DC motor is OK or not?

2021-12-19 22:29:40 Volcano Motor Read

Before testing the DC brushless motor, prepare a multimeter, check whether the multimeter is available, and then adjust it to the appropriate gear.

First of all, use a multimeter to measure whether the three phases of UV, UW and VW are all on. If there is a DC resistance path reaction, there is no disconnection.

Secondly, connect the UV, UW and VW to the oscilloscope respectively, and turn the DC brushless motor by hand to see if there is any output waveform similar to sine;

Step 3, if there is a Hall motor, supply 5V DC to Hall, and turn the DC brushless motor by hand to see if the waveform output by Hall is correct.


If there is no oscilloscope and 5V DC power supply, you can directly use the multimeter voltage file and connect it to both ends of the lead of the DC brushless motor to rotate the DC brushless motor. Because the rotation of the DC brushless motor will generate induced voltage, the multimeter will indicate the voltage.  

Testing from the operating principle 

The manufacturer of brushless DC motor tells the working principle and maintenance of the controller. When the knob is turned, the speed control signal is sent to the main processing chip in the controller through the lead wire. The main processing chip in the controller responds according to the received signals, sends control signals and drive signals to logic circuits and power transistors, and then outputs motor control and drive signals to make the brushless motor run.


After the motor rotates, its internal position sensor (namely Hall element) will detect the position signal of the rotor magnetic pole and feed it back to the main processing chip in the controller to control the on and off state of the corresponding power transistor.


When the brake handle is pressed, the brake signal of the brake handle is sent to the controller through the connector. After the signal is processed by the main processing chip in the DC brushless motor controller, the output brake signal makes the power transistor in the off state, so that the brushless motor is powered off and the purpose of braking is achieved.


In the process of controlling the electric bicycle, the main processing chip displays the current control signals in the indicator through the connector.


In order to know the working principle of brushless motor, it can be divided into several main functional circuits, such as power supply circuit, starting circuit, braking circuit, speed control circuit, under-voltage protection circuit and over-current protection circuit.


The controller and the brushless motor are usually linked by three thick leads and no thin wires. In the DC brushless motor, the thick leads are the three phase wires connecting the controller and the motor, and the thin five leads are the leads connecting the controller and the motor Hall element. The terminal voltage of the leads can be detected by a multimeter. 

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