Capacitor help or hurt.

7 posts / 0 new
Last post
sean
Offline
Last seen: 11 years 5 months ago
Joined: Friday, February 9, 2007 - 19:38
Points: 12
Capacitor help or hurt.

Would a 1fared cap between the motor and controller (etek and AXE) help or hurt the performance?

Fechter
Fechter's picture
Offline
Last seen: 11 years 9 months ago
Joined: Friday, November 17, 2006 - 07:01
Points: 199
Re: Capacitor help or hurt.

Hurt.
You wouldn't want to put a capacitor there because it would shunt the inductance of the motor which is needed in order for the controller to work at partial throttle. An Etek has very low inductance to start with, which may cause problems with some controllers if the switching frequency is too low. It may actually help to put an inductor in series with the motor.

You could put the cap across the battery and it would help a bit, but it's probably not worth it.

sean
Offline
Last seen: 11 years 5 months ago
Joined: Friday, February 9, 2007 - 19:38
Points: 12
Re: Capacitor help or hurt.

I ask for an electrathon car on a go-kart track, any thing would help since most ever thing else is equal. A lot of acceleration and slowing. Two optima red tops and etek or prem and an AXE 400 amp controller we average about 1.1 hp on need to run for one hour at about 40 mph. looking for any edge that would help.
Thanks
Sean

Fechter
Fechter's picture
Offline
Last seen: 11 years 9 months ago
Joined: Friday, November 17, 2006 - 07:01
Points: 199
Re: Capacitor help or hurt.

In that case, a capacitor across the batteries can't hurt. It will reduce resistance losses in the batteries and Peukert effect.

An inductor is a bit trickier. It would need to handle the peak current without having much resistance, and yet still have some inductance. Something like a big torroid with many parallel windings of heavy copper. I'm not sure how much an inductor would help, but the inductance of the Etek is so low that the flux could max out during the switching cycle of an Alltrax. You would have to balance any gains from more efficient switching against the resistance of the inductor. If you could jack up the switching frequency a bit higher on the controller it would reduce the required inductance. This might be programmable.

sean
Offline
Last seen: 11 years 5 months ago
Joined: Friday, February 9, 2007 - 19:38
Points: 12
Re: Capacitor help or hurt.

Fechter: Higher switcher freq. Cool. Do you think this is reasonably possible to do with the alltrax AXE400?
Thanks

Fechter
Fechter's picture
Offline
Last seen: 11 years 9 months ago
Joined: Friday, November 17, 2006 - 07:01
Points: 199
oops

oops

Fechter
Fechter's picture
Offline
Last seen: 11 years 9 months ago
Joined: Friday, November 17, 2006 - 07:01
Points: 199
Re: Capacitor help or hurt.

I can't remember if that's an option with that model. I know some controllers have adjustable switching frequency. I think you can download the spec sheet from the Alltrax website.
I don't know what the optimum switching frequency would be for the Etek, but I would estimate around 40khz or higher .
This would not make any difference at full speed since it's not switching anymore.
At low speeds and during acceleration it might make a noticeable difference.

Log in or register to post comments


Who's online

There are currently 0 users online.

Who's new

  • hippidave
  • rvair19
  • Nicosp
  • VoltLurker
  • Greatwhite

Customize This