motor is drawing more current than expected

[hashiR]

Hello all,

I’m using NUCLEO F302R8 and IHM08M1 for motor control. While the motor runs, it gradually heats up to around 85°C and draws more current than its rated value in no-load conditions.

while using the IHM07M1, the motor's heating seems normal, but the board temperature rises significantly.

What could be causing this issue?

[hashiR]

Thank you for your response.

I’ve tried both sensorless and sensored FOC. but the motor heating issue persists with both control methods. I also tested a 6-step algorithm, but the problem remains the same.

Are BEMF waveforms important for Hall-based FOC?

I’m attaching the motor datasheet below.

[unsigned_char_array]

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You could spin the motor by hand or by a (cordless) drill and measure the HALL output and the BEMF. HALL sensors should produce 120 degree rotated waveform and so should the BEMF. The BEMF of one phase can be measured by using 3 resistors (1k for instance) connected to each winding to get a virtual ground if the windings are connected in star.
I suspect the HALL sensors may need to be calibrated due to mechanical tolerance. If they fire too soon or too late the controller might switch the outputs at the wrong time.

[hashiR]

Hi @unsigned_char_array 

I tested the same motor with another controller from Maxon, and it operates correctly, drawing only the expected no-load current of 210mA.

However, when using my current controller, the motor exhibits excessive heating, even when using a sensorless algorithm. The overheating persists regardless of whether I use a sensored or sensorless approach.

Do I need to recalibrate the Hall sensors? If the issue occurs with both sensored and sensorless algorithms, what could be causing the overheating, especially when the motor works smoothly with the Maxon controller?

[unsigned_char_array]

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@hashiR wrote:

Hi @unsigned_char_array 

I tested the same motor with another controller from Maxon, and it operates correctly, drawing only the expected no-load current of 210mA.

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So we can exclude the motor as the cause. Though the HALL sensors could be wired incorrectly, but I suspect that then the motor would not spin at all.

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@hashiR wrote:

However, when using my current controller, the motor exhibits excessive heating, even when using a sensorless algorithm. The overheating persists regardless of whether I use a sensored or sensorless approach.

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I suggest sticking to sensored for now as that should be easier to measure as BEMF is noisier.

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@hashiR wrote:

Do I need to recalibrate the Hall sensors? If the issue occurs with both sensored and sensorless algorithms, what could be causing the overheating, especially when the motor works smoothly with the Maxon controller?

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Calibration of the HALL sensors is adding a phase correction, this can be done mechanically or in software. I don't know if the algorithm you use can self calibrate or requires external calibration values.
If the controller switches too soon it will brake the motor part of the time heating it up.

The easiest way I think you can test is to compare the output of the Maxon controller w.r.t. the HALL signals compared to the IHM08M1 output w.r.t. to the HALL signals.