Q85 motor BMSBattery Square Wave or SineWave??

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casainho
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Q85 motor BMSBattery Square Wave or SineWave??

Post by casainho » Jun 01, 2017 12:46 pm

I am being trying to run BMSBattery Q85 motor with my firmware as 6 steps and SVM for a possible FOC. I also have BMSBattery S06S controller to run this motor.

What I found (with no load):
- 6 steps gives the less noise and less current (1.8A at 30V and max speed)
- sinewave from S06S controller gives more noise and higher current (2A at 30V and max speed). Also the voltage increases on the power supply, from 30V to 31V!!
- SVM for FOC, gives even more noise, runs slow and higher current like (6A at 30V and max speed). Also the voltage increases on the power supply, from 30V to 34V!!

Does anyone knows why this happen?

I put a 3 resistors in a start connection and connect to each motor phase, turn by hand the motor and the BEMF voltage shape is sinewave so I would expect that this motor should run with a sinewave/FOC...
Developer of OpenSource firmware for EBike BMSBattery S/Kunteng KT motor controllers: https://opensourceebikefirmware.bitbucket.io/

d8veh
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Re: Q85 motor BMSBattery Square Wave or SineWave??

Post by d8veh » Jun 01, 2017 4:59 pm

In all the tests I did with these motors, the no-load current was about 1.0 amps.

casainho
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Re: Q85 motor BMSBattery Square Wave or SineWave??

Post by casainho » Jun 02, 2017 12:39 am

The questions are: why the original firmware of S06S (sinewave) controller makes the motor rotating with more noise, takes more current and the power supply voltage increases when a more simple way to run the motor with 6 steps (my OpenSource firmware) make less noise, uses less current and the power supply voltage don't change as expected????
And another way to control that I am trying with my OpenSource firmware, that is even more advanced than sinewave, gives even much more noise, takes much more current and increases much more the power supply voltage!!

I have some clues. The mosfet drivers are called "inverter" and as on DC-DC converters, the inverter can boost the voltage make it much more bigger than input voltage. The 6 steps uses PWM ON and the low side mosfets are always ON/OFF with no PWM. The other modes like sinewave have PWM in low side mosfets... I think the issue is a wrong dead time between high side mosfets and low side, that short circuit the motor windings or mosfets a bit and that will boost the voltage (thanks also to the capacitors on the board) but also asks more current from the power supply and will make the noise on the motor.

I will try to play with the dead time configuration on the firmware/microcontroller but I don't know what are the limitations of the board/mosfet drivers...

I already measured the dead time of original firmware:
Image

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More info here: https://opensourceebikefirmware.bitbuck ... gnals.html
d8veh wrote:In all the tests I did with these motors, the no-load current was about 1.0 amps.
Thanks!! The current seems to depend on the voltage, like 36 or 48v uses less current... also on the motor gear ratio, I guess my motor the the highest.
Developer of OpenSource firmware for EBike BMSBattery S/Kunteng KT motor controllers: https://opensourceebikefirmware.bitbucket.io/

d8veh
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Re: Q85 motor BMSBattery Square Wave or SineWave??

Post by d8veh » Jun 02, 2017 3:54 am

There's a paramater in the S06S that you have to change to match the motor. It's P1 = qty of magnets x reduction ratio. There's also another parameter somewhere that has something to do with phase angle and sequence that has remained a mystery. If you could find out what these parameters actually do, you'd make several forum members very happy.

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