Weird dutycycle.....

Discussions regarding the Field Oriented Control (FOC) implementation on the VESC.
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Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Weird dutycycle.....

Postby rew » 14 Feb 2017, 17:23

I have a motor that I want to run in FOC mode. Measuring the parameters seems to be difficult. I can't seem to be able to get it to spin up with the "measure lambda" button. With a bit of help I've managed to get one successful measurement. So now I have the 25mOhm, 195 uH, lambda=0.011 stored in my archive, and I can attempt to run the motor.

Anyway, in BLDC mode, I can get the motor to run starting at 1.5A. It needs a push to get started, but then it will spin up to maximum speed for the voltage. In FOC mode I seem to need a LOT more current. At around 20A the motor starts nicely and accelerates to the maximum speed a bit faster than with the 1.5A in BLDC mode. (but not 10 times faster as you'd expect).

Anyway, then at 95% dutycycle, the motor current remains at 20A, but the battery current does not satisfy motor current times dutycycle. I seem to get about 2A - 3A of battery current.

Another odd thing is that when I hit "release motor", the dutycycle jumps to 240% !

BLDC_TOOL_odd_dc.png (149.64 KiB) Viewed 564 times

These effects, could this mean that the lambda measurement is wrong and that I should maybe increase or decrease the value?

Update: I thought maybe there IS somethign odd with the RPM going on. But I just measured the RPM and my motor runs at 2200ERPM as normal at 24V (6 pole pairs -> 366 real RPM, a KV of about 15).

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