Sounds OK. I grok transformers and oscillating currents.
On Sun, Mar 9, 2014 at 1:43 AM, Roger Stockton <rstock...@delta-q.com>wrote: > Michael Ross wrote: > > > " battery amps would be lower than motor amps at low RPMs" > > > > That sounds like nonsense to me, but I don't have the whole circuit > > in front of me. > > It is absolutely correct. The PWM motor controller behaves similarly to a > variable transformer, but with DC input and output. > > DC motor RPM is proportional to voltage; at low motor RPM, the battery > pack voltage is reduced by the motor controller so that less than full pack > voltage is applied to the motor. > > Aside from a relatively small loss due to inefficiency of the controller, > power out to the motor is (approximately) equal to the power into the > controller from the battery. > > Assume the battery does not sag so we have full pack voltage into the > controller and further assume that the voltage applied to the motor is half > of the pack voltage. For approximately equal power in and out of the > controller, the current in the motor loop will be twice that in the battery > loop. > > As long as the voltage at the motor is less than the battery voltage, the > current in the motor loop is greater than that in the battery loop. Once > the motor voltage (speed) increases to the point of being equal to the > battery voltage, the motor current and battery current are equal. > > Cheers, > > Roger. > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140309/654b552c/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
