How to calculate the Ke?

[gtop.1]

I refer here：https://wiki.stmicroelectronics.cn/stm32mcu/wiki/STM32MotorControl:How_To_manually_configure_the_motor_parameters 

Below is the profiler's result. Ke=9.59 Vrms/kRPM.

Below is my owm test.

Vpp=13.6v，pole pairs=5，fbemf=83.33Hz. Ke=(13.6*5*1000)/(2√2*83.33*60)=4.8085 Vrms/kRPM.

I wonder if I chose the wrong frequency？Is it between point A and point B or pointA and pointC?Thanks.

[cedric H]

Hello @gtop.1,

The frequency you chose is correct. I would be more in favor of definition issue regarding the pole pairs number to explain your factor 2 difference between the profiler output and your computation. 

Regards

Cedric

[gtop.1]

My motor ' poles is 10 (pole pairs is 5). Do you mean that calculate the Ke should use the poles not pole pairs?

[cedric H]

If you look at this documentation  How To manually configure the motor parameters - stm32mcu

Paragraph  2 Pole pair (number) parameter .

It is stated :

• The number of rotor stable positions in one mechanical turn represents the number of pole pairs.

So if you have 10 stable positions, then your pole pairs number must be 10.

Regards

Cedric

[gtop.1]

Unfortunately, it have 5 stable positions.This confuses me and I don't know what the problem is.

[gtop.1]

Is there any other possibility？

[cedric H]

Could you describe accurately how did you generate the oscilloscope dump ? 

How did you spin your motor for instance ? 

Cedric

[cedric H]

Hello @gtop.1,

No news ?

how did you spin your motor to generate your waveform, did you plug it to any electronic other than the scope ?

Cedric