The problem of DC brushless motor UVW waveform without Hall connection

chenbingjy

The problem of DC brushless motor UVW waveform without Hall connection [Copy link]

Our company wants to make a washing machine with a 310V DC motor. I bought a development board, but it turned out to be a closed loop, so I tried to change it to an open loop.

But the motor doesn't turn. The hardware guy asked me to power the IGBT, and then connected 5V to the 310V.

Let me see if the UVW three-phase waveforms are 120 degrees apart. The result is that, as shown in the figure above, they are in phase. This shows that there is something wrong with my program.

But I don't know where the problem lies. Is it because the commutation is not successful or some other reason? Can someone help me analyze it? Thank you!

qwqwqw2088

Is there a problem with the program?

Let's analyze the problem.

chenbingjy

qwqwqw2088 posted on 2022-1-29 08:53 Is there a problem with the program? We need to analyze which part has the problem

Thank you! Today the hardware guy asked me to short out an unsoldered resistor and test it again.

The resulting waveform becomes like this

In addition, the motor is connected.

chenbingjy

I changed the program again and the wave formed like this.

chenbingjy

chenbingjy posted on 2022-1-29 10:48 I changed the program again, and the wave is formed like this.

After burning this part of the program, the motor can rotate, but it is not smooth and it is intermittent.

Fred_1977

What is a brushless motor?

powsun

Good brushless motors usually have a Hall circuit to determine the rotor position, which can start better and run smoothly. Good Hall plates use gallium arsenide and indium antimonide, such as AKM (Asahi Kasei) EW-400series Ultra-high sensitive supply voltage 3~26v

If there is a domestic replacement, you can apply for a sample

javnson

It is recommended that you conduct the analysis in the following steps:

1. Disconnect the drive part, IGBT and other parts, and only keep the development board, main control board or core board;

2. Use an oscilloscope to observe the relationship between the three-phase signals of the motor drive. Specifically, observe whether one PWM output is normal, whether there is any jamming (caused by interrupt interference, incorrect priority, etc.), observe whether one bridge arm (two PWM outputs) is normal, whether the amplitude is correct, and whether the dead zone is correct (special attention should be paid here to whether the dead zone of the dead zone software matches the parameters of the IGBT, otherwise it may cause a short circuit and hang the tube after the power is strengthened later), and then observe the upper or lower bridge arm of the three phases at the same time. Under normal circumstances, three waveforms of 3*120° should be obtained, which are staggered with each other. (If the output is incorrect, then the basic logic of the program is indeed wrong. This problem is relatively low-level, but it is certain that if it is wrong here, then the logic of the program is definitely not reasonable. If it is convenient for the host, you can post this part of the code for me to see, or you can send it to me privately)

3. If the above tests are met, connect the IGBT driver chip and power on the driver chip. Generally, a 12V or 15V driver power supply can be directly soldered to it by pulling a wire from the outside. First, observe whether the same port is synchronized after being driven by the IGBT (asynchronous may mean that the driver chip is not connected correctly, or the logic of the driver chip and the output GPIO logic are incorrect, such as IR2103 is more likely to make this mistake). Then repeat the above steps to observe whether the output signal of the IGBT driver chip is correct.

4. Then apply a weak voltage to the IGBT, which should be slightly higher than the driving voltage of the motor driver chip. This way, it can be observed more clearly, and several levels can be staggered. Observe the synchronization and voltage. The logic of the entire observation is the same as above.

5. Make sure that the waveform output by the IGBT is the desired waveform before adding the motor. Otherwise, the abnormal operation of the motor may make the waveform difficult to understand. There are many specific situations, so I will not go into details. If you are really interested, you can refer to the relevant monographs on motor transient analysis, and deduce it with a little knowledge of power electronics.

The above is a simple framework, you can try it. Directly adding 5V is generally not effective in testing power electronic circuits. For example, the waveform above may indicate that the IGBT is not working in the saturation region, but may still be in the linear region or floating in some strange place.

2782429981

Hello, where did you buy your development board and what driver is it? I also want to make a brushless motor.