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BLDC Motor Drive waveforms

  • Thread starter Harry Dellamano
  • Start date
H

Harry Dellamano

Jan 1, 1970
0
Attached is a waveform of one winding of a three phase trapezoid drive
motor with another phase PWM drive on the bottom. This 3 phase 4 pole motor
is rotating at 1500 RPM with 120Vdc, 20KHz and about 8.0 amps peak on each
winding. My drive electronics but someone else's (enemy) software.
https://www.dropbox.com/s/p7yg8peujjkzvac/DSX_20130802022721.pdf
My question, does that current waveform, on top, look correct? At 3k RPM it
screams. Should not the top portion and bottom be similar?

Regards, Harry
 
H

Harry Dellamano

Jan 1, 1970
0
Tim Wescott said:
It doesn't look to me like the problem is that the half bridges are or
are not conducting -- it looks to me like the problem is that the
sequencing isn't right.

Tim, you are the man! The sequence is fudged up. It should be at any driver
output; 2/6 PWM, 1/6 float, 2/6 low to sink current, 1/6 open, then repeat.
Mine has 1/6 low, 2/6 PWM, 1/6 float, 2/6 low. That is 3/6 low and only 1/6
float. What a POS!
Thanks Tim, Harry
 
H

Harry Dellamano

Jan 1, 1970
0
Harry Dellamano said:
Tim, you are the man! The sequence is fudged up. It should be at any
driver output; 2/6 PWM, 1/6 float, 2/6 low to sink current, 1/6 open,
then repeat. Mine has 1/6 low, 2/6 PWM, 1/6 float, 2/6 low. That is 3/6
low and only 1/6 float. What a POS!
Thanks Tim, Harry
Here is a pic of current in one of the three phases from my crack software
weenies.
https://www.dropbox.com/s/sx7xn6m6w6mw60r/2000rpm 270V 775W Phase U.pdf

This trapezoidal waveform has ripple current on the positive and negative
peaks causing torque chatter. The SW boys say that is normal. (Sorry for the
current offset in the pic. poor tech)
What say anybody?

Thanks Harry
 
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