You are here

is Cross Coupling power limitation?

7 posts / 0 new
Last post
ziumus
Offline
Last seen: 2 years 6 months ago
Joined: 2018-09-14 10:33
Posts: 24
is Cross Coupling power limitation?

Hello,

I'm unable to get more power from the motor.

Example :

QS 205, can get max 12kW ,

QS 138 70H can get max 18kW .

the test was done with the same power settings, same controller,and same battery,just different detection motor parameters.

72v battery capable of 400amps.

increasing phase current limit above 450A does not make more power, but low speed torque is much higher.

with another brand controller, i can have 16kW on qs205.

I know that 16kW on qs205 does not make sense because of overheating, but just what to know why I cannot get that with vesc for a short period.

All tests are done with hall sensors on start, and after 2500 eerpm sensorless.

Noticed when i use encoder whole rpm range power is 15% less than using observer.

Is that problem connected with motor saturation, observer algorithm, or something else?

also tried to play almost all settings in vesc tool, main focus was on detection settings,and saturation setting with no success.

does anyone have an idea, what could be the problem?

 

 

 

 

 

 

 

skyline1970
Offline
Last seen: 5 months 1 week ago
VESC Free
Joined: 2017-09-07 22:28
Posts: 232

You could try with just bldc mode.

ziumus
Offline
Last seen: 2 years 6 months ago
Joined: 2018-09-14 10:33
Posts: 24

tried bldc, but bldc works very inefficient, and unreliable,

tried playing with encoder offset, and when i put manually 30angle offset, i get the same power as the observer

don't know what is a problem, also why with encoder have less power ?

after 65% speed phase amps start to go down,i guess the amps should only drop at the end of the duty cycle.

 

skyline1970
Offline
Last seen: 5 months 1 week ago
VESC Free
Joined: 2017-09-07 22:28
Posts: 232

in fact, in perfect configuration, slowly acceleration should not make enormous change in current, just increasing in speed. Decrease in current shows that the motor has much more relaxation. And BLDC mode should provide much more power because of shape of the driving signal form (trapezoid). Foc mode driving signal form is like sinusoidal.

ziumus
Offline
Last seen: 2 years 6 months ago
Joined: 2018-09-14 10:33
Posts: 24

When Phase amps starts to increase, my D axis voltage start to decresse to -20V.

I guess because of the very low Vd voltage + bemf, it is not possible to push more amps, is it possible to overcome that?


 

 

district9prawn
Offline
Last seen: 2 years 1 week ago
Joined: 2018-04-26 12:18
Posts: 123

From what you have described here and your plots from your other thread, I think your encoder offset might be a bit off.

In any case, I would recommend setting the sensorless rpm to a low value even when using the encoder, rather than using the encoder over the entire rpm  range.

ziumus
Offline
Last seen: 2 years 6 months ago
Joined: 2018-09-14 10:33
Posts: 24

angle offset is from detection, tried many times.

yes it works better when i manually set  offset.

but with observer works better,

is observer more accurate than encoder?