The problem of brushless DC motor without Hall no-carry waveform

chenbingjy

The problem of brushless DC motor without Hall no-carry waveform [Copy link]

 

I found this waveform on the Internet.

But when my program is not connected to the motor, only the U phase has a waveform. The V phase waveform and the W phase waveform are available at the beginning. As long as my hand moves close to the RUN/STOP,

The waveform is gone.

What is going on? Is this interference? Thank you!

chenbingjy

I was wrong. The V and W phase waveforms only last for a short time, a few seconds.

chenbingjy

My understanding is that back EMF zero crossing detection is not possible with no load.

Therefore, the V phase and the W phase cannot last long.

I don’t know if it’s right.

Please give me some advice

qwqwqw2088

Zero-crossing detection is the detection of voltage peak value, or zero-point voltage detection

No load

qwqwqw2088

As soon as your hand moves towards RUN/STOP,

The waveform is gone.

What's going on? Bad contact? Is there interference?

chenbingjy

qwqwqw2088 posted on 2022-1-24 15:17 As soon as my hand approaches RUN/STOP, the waveform disappears. What's going on? Is the contact bad? Is there interference?

No, I later discovered that it only lasted for a few seconds.

chenbingjy

qwqwqw2088 posted on 2022-1-24 15:16 Zero-crossing detection is the voltage peak value detected, or zero-point voltage detection has nothing to do with no-load

The IGBT is not turned on yet. There is no connection in the middle.

I tested the development board I bought and it was the same situation. Only the U phase was always there, and the V and W phases only lasted for a few seconds.

But it can rotate when connected to a motor.

chenbingjy

Under normal circumstances, if the PWM wave and IGBT are not connected, will the waveform be like the one in the original post? Thank you

chenbingjy

qwqwqw2088 posted on 2022-1-24 15:16 Zero-crossing detection is the voltage peak value detected, or zero-point voltage detection has nothing to do with no-load

What I understand should be the zero point of the back EMF voltage.

Without a motor connected, the back EMF cannot be detected

qwqwqw2088

The picture on the first floor shows three rotor position signals

Without connecting the motor, the back electromotive force cannot detect the motor's status signal.

The motor status signal controls forward, reverse and braking, and then outputs to the drive circuit through PWM to control the on and off of the IGBT.

chenbingjy

qwqwqw2088 posted on 2022-1-24 16:01 The first floor diagram shows that if the three-way rotor position signal is not connected to the motor, the back electromotive force cannot detect the motor's status signal. The motor's status signal controls the positive and ...

Thank you! I'll think about it.

chenbingjy

qwqwqw2088 posted on 2022-1-24 16:01 The first floor diagram shows that if the three-way rotor position signal is not connected to the motor, the back electromotive force cannot detect the motor's status signal. The motor's status signal controls the positive and ...

Can I assume that if the motor is not connected and the state change signal cannot be detected, there will be no phase change?

So only one phase has a waveform.

2782429981

Hello, can you recommend a development board? I also want to try the Hall-less brushless motor driver.

chenbingjy

2782429981 Published on 2022-4-20 14:38 Hello, can you recommend a development board? I also want to try the Hall-less brushless motor driver

Taobao has