Increasing inductance slows down the ramp up of current, so adding inductance to a motor with too low inductance helps to get better current limit, especially on controllers with low switching speed where a single step will cause so big current change that it can damage the controller.This is entirely different from the addition of a physical loop of wire, even though that also adds inductance, because a physical distance between the two wires or even a wire running without the "return" current running right next to it, will act as antenna, spewing the switching noise into the air and possibly disrupting the operation of sensitive circuits in the controller but certainly killing your radio reception and possibly someone else's which is illegal. The addition of inductance is what i have done on my previous EV truck which had a low speed EV100 controller and a large 11 inch motor. I could fit 3 loops of the motor cable through a large microwave transformer core. But i kept the motor cables close together. Do not add resistance in the motor loop, as that only increases losses.Hope this clarifies.Cor
Sent from my T-Mobile 4G LTE Device -------- Original message --------From: EVDL Administrator via EV <[email protected]> Date: 12/17/17 9:13 AM (GMT-08:00) To: Electric Vehicle Discussion List <[email protected]> Cc: EVDL Administrator <[email protected]> Subject: Re: [EVDL] DC controller common terminal Cor, Paul, thanks for the replies! I forgot about the freeewheeling diode(s). So I'll connect it the way the manual says. Still ... I recall some discussion years ago about fixed frequency 15kHz+ Curtis controllers having trouble with current limiting on large, low inductance motors. It caused the combination to have jerky starts, or worse. The way Lee Hart explained it was that the low resistance meant that the current didn't have time to decay enough when the chopping transistors were off (because it was a very short time), so the current just kept rising insead of being properly limited. If that were the crucial factor here, I would think that extra resistance in the motor loop would HELP. But obviously not, because we're always advised to keep the motor leads as short as possible. I hate to sound dense (even though I am), but while I can understand that connecting the motor lead at the contactor (or other point ahead of the controller common terminal) could change the way the controller "sees" the motor, I still don't fully understand what specific problems that might cause. Maybe the earlier discussion about motor loop impedance / resistance isn't relevant here? Thanks again! David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20171217/1676c7ab/attachment.html> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
