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InstaSPIN FOC BLDC - Phase Current Waveforms

stomp
Genius 4705 points

Hi,

I have a custom board based on the HVKit, with the difference being my own gate driver and FET's as opposed to an all-in-one module. The CPU is F28027F. We have had the motor running nicely on the HVKit, and have now transitioned to custom hardware.

I've been having a lot issues with the FET's switching. I have "fine tuned" my application and can achieve 200RPM, but the current waveforms are really bad, and I cannot understand "why" I would be seeing these sorts of waves.

I am taking my current measurements for each phase at the input points into the CPU.

My board is setup for 20A (+/-10A) same as HVKit.

At 100 RPM with VDC = 30V, I have the following Phase-U voltage (CH2) and Phase-U Current into the ADC (CH1).

And when zooming in on the rising edge of the phase voltage I note that the phase current is rail-to-rail. (indicating +/-10A) 

Finally my design should run at a DC bus of > 200V. I'm just running it at low voltage for some basic tests.

If I run the design at VDC > 200V I have the top Phase U FET get super hot, while the rest are cool.

I could be looking at a hardware problem, some gate switching issue.

Can anyone lend some advice.

Thanks

Stomp!

  • 0
    TI__Guru** 117130 points
    It seems the current doesn't sample well in your board. Please monitor 2 PWM channels (Such as U+, V-) and the active phase current (V ) in the same time. And check whether the current sample deal circuit is right, and accord to your code.
  • 0 in reply to Yanming Luo
    Genius 4705 points

    Hi,

    Actually, this raises a question.

    There is some signal delay in the MOSFET system which includes:  Overlap Protection delay, gate driver delay, PWM dead-time, etc.

    Do you know if it is possible to change the ADC sample point / window in InstaSPIN so as I can ensure the I and V samples are taken at the correct time?

    Thanks

    Stomp!