High-Speed BLDC Motor Heating and Excess Current Draw (No Load)

[hashiR]

Hello,

I am experiencing an issue with my high-speed BLDC motor (47,000 RPM, 24V, 180W). Even when running the motor with no load, it is heating up more than expected, and it is drawing more current than the no-load current specified in the motor's datasheet.

I am using the IHM08M1 motor driver along with the Nucleo F401RE to drive the motor. Could anyone help me understand why the motor is behaving this way? What could be causing the excess current draw and overheating, even when no load is applied?

I would appreciate any guidance or suggestions on how to resolve this issue.

Thank you!

 

[hashiR]

anyone here?

[GMA]

Hello @hashiR,

I suppose that these posts (motor is drawing more current than expected and motor taking more current) are related to the same topic?!
According to the attached motor datasheet, the maximum temperature is 125°C, then 85°C is not out of range.
Using IHM07 power board, you will have a maximum provided current equal to 2.8 A, and 30 A from IHM08, this is the reason in one case Power Board is heating up and in the other case it is the motor. You can confirm it by measuring motor currents with both power boards.

What is the measured no-load current? Does this no-load current is measured at maximum speed? What is the expected value?

 

[hashiR]

Thank you for your response.

The no-load current specified in the datasheet is 210 mA, but the motor is drawing 1A, resulting in significant heating—reaching 70°C within just 3 minutes of operation. I confirmed with the motor manufacturer that this level of heating is abnormal.

I’ve tried both sensored and sensorless FOC, but the heating issue persists in both cases. I even tested a 6-step algorithm also .

motor operates correctly, the overheating problem remains.

What could be causing this excessive heating?

 

[GMA]

Hello @hashiR,

Just two remarks:
- Are you using Flux Weakening feature? It will add an Id component that could create this current (see user manual, Flux-weakening control chapter).

- In IHM08 User Manual documentation, it is mentioned in "2.2 Building the system" chapter that "For FOC control, set jumpers: JP1 and JP2 closed, J5&J6 on the 3-Sh side. Remove capacitors C3, C5 and C7"

[hashiR]

Hi @GMA,

• I am not using the flux-weakening feature.
• I have ensured the correct hardware modifications are implemented.

I tested the motor with another controller from Maxon, and in that case, the motor only draws its specified no-load current as expected. However, when using the IHM08M1, the motor exhibits excessive current draw and overheating.

What could be causing this issue with the IHM08M1?

[hashiR]

is any one here