If you want to see a pic of the controller that is in the Henney Kilowatt that was ours and is now Mark Farver's here's a link:
http://intrepid-travelers.com/images/henney-controller-1024.jpg /Aaron Choate On Tue, Jan 15, 2013 at 9:26 PM, Lee Hart <[email protected]> wrote: > On 1/15/2013 11:35 AM, Klaus wrote: > >> I recall seeing a picture of a mechanical PWM controller comprising of a >> segmented copper disk being spun by smaller electric motor. Two brushes >> that could be moved relative to one another sat side-by-side on the disk >> making for PWM control. I can only imagine the shower of sparks it >> created >> running an electric motor for the little while it lasted, unless they had >> some heroic snubber across it. >> > > This idea has surfaced many times. It gets tried, and fails. Arcing is > *tremendous*, and the contacts soon wear out. > > A snubber is vital to get it to work at all (for hours, instead of > minutes). A freewheel diode helps a lot more (days, instead of hours). > These weren't available until the last 20-30 years; before that, every > mechanical chopper was a reliability headache. > > There are a lot of very sophisticated design tricks that have to be used > to make this kind of mechanical switch-based chopper last long enough to be > at least marginally useful. The usual backyard inventor types usually miss > this. > > One trick is synchronous resonant switching. The circuit is arranged so > the switch opens and closes at zero current and/or voltage. This was used > in the 1950's car radio vibrators, to step 6vdc up to 250vdc for the vacuum > tube radios. > > The commutator in a DC motor uses these tricks as well. It's designed so > the voltage is zero as the brush crosses from one commutator bar to the > next. > > -- > The trouble ain't that there's too many fools, but that lightning ain't > distributed right. -- Mark Twain > -- > Lee A. Hart, > http://www.sunrise-ev.com/**LeesEVs.htm<http://www.sunrise-ev.com/LeesEVs.htm> > > ______________________________**_________________ > UNSUBSCRIBE: > http://www.evdl.org/help/**index.html#usub<http://www.evdl.org/help/index.html#usub> > http://lists.evdl.org/**listinfo.cgi/ev-evdl.org<http://lists.evdl.org/listinfo.cgi/ev-evdl.org> > For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/* > *group/NEDRA <http://groups.yahoo.com/group/NEDRA>) > > -- http://www.aaronchoate.com @aaronchoate +Aaron Choate facebook.com/aaronchoate University of Texas Libraries: http://www.lib.utexas.edu REVOLT: http://www.revoltev.com EVTradinPost: http://www.evtradinpost.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130116/b8407f01/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)
