On 18 Jan 2013 at 7:35, Christopher Darilek wrote: > I plan to use one of these old PMC controllers in my conversion ... It does > indeed use > transistors, at 1kHz chopping frequency. ... > > http://4.bp.blogspot.com/-DPY4sZajcTA/UPlnYhw-uOI/AAAAAAAAALY/ZkpKU-eMQ0M/s160 > 0/CurtisPMC.png
That looks like the old PMC DCC-96, which came in a more or less shoebox- shaped package. Mine was green. I used it in a Comuta-car. It had originally been fitted to a Bradley GT. I think I recall being told many years ago that the current limiting circuit for these controllers measured the voltage drop across the transistors (or maybe just one of them; I'm too lazy to look at the schematic right now). As the transistors age, their resistance rises, and the available current from the controller thus falls. However, if you try to crank up the current limit, you're apt to blow the transistors. So you just have to accept less power in an aging controller. I'd also be inclined to replace the caps before trying to use it. You're talking about ~35 year old hardware here. I think the problem is that the ESR rises with age, but I'm no engineer; Lee Hart can probably tell you more. BTW, the DCC-96 manual I have here says it chops at 4kHz, not 1kHz; maybe yours is even older than mine was. Or maybe you have a DCC-72? I didn't think there was much difference. FWIW, my later PMC-25 chopped at 2 kHz. I should scan this DCC manual for the EVDL library one of these days. I have the schematic up there, but not the rest of the manual. 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 For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
