Not sure how the old Seattle trolleys used to work. I understand they ran (and still do) on 600VDC. The current fleet (dating back about 30 years) is very smooth.
I would presume the motors were DC and I recall that the the acceleration was very "lurchy". It seemed that there were different pedal positions that jumped to different power levels. Perhaps there were a bunch of contacts and different amounts of motor windings that were connected depending on pedal position? Peri -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Dwain Swick Sent: 14 January, 2013 1:45 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] What did EVs do before today's motor controllers? The early golf carts used a board with a series of three large resistors. They were mounted to to copper bolts and a copper wiper moved over the bolt heads. The first position the current went thru all three resistors and the next position, thru two resistors and so forth. This gave you four speeds. When you pulled a lot of current, the resistors would really glow red. Very inefficient, lots of KW's heating air. I built a lot of those,some with double resistors on each position and some with more positions.. I was building electric tugs for moving airplanes Dwain Swick kansasev.com --- On Mon, 1/14/13, Bruce EVangel Parmenter <[email protected]> wrote: From: Bruce EVangel Parmenter <[email protected]> Subject: [EVDL] What did EVs do before today's motor controllers? To: [email protected] Date: Monday, January 14, 2013, 2:26 PM [ref electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-CBC-TV-Murdoch-My steries-built-their-own-EV-for-season-5-tp4660513.html ] I found it interesting to see what EVs did to control the current to the motor before the EV community could use the controllers created after affordable power IGBT became available on the market. A long time ago, I had trailer-ed my Blazer EV up to Sacramento (160 miles away from home, long before there were public EVSE to use to get there). Sacramento's Utility (at the time) was way-way ahead of everyone else. They had a solar panel array that covered the parked EVs that were charging. The arrary fed the same grid that the EVs were drawing from. That does not sound so impressive today because it is fairly common place, especially in OR and WA, but it was one of the first one in CA http://www.ecotopia.com/st/images/pvevchg.jpg With my Blazer fully charged (fat-n-happy) off SMUD's solar electrons, I went and hung out with the Sacramento EAA folks (they called themselves SEVA, but do not confuse them with Seattle's Chapter). They had one member that had bagged a nice metallic gold colored triumph spitfire donor that looked something like http://www.cargurus.com/Cars/1980-Triumph-Spitfire-Pictures-c11820_pi2081386 3#pi9911552 He had the top down, and had mounted a large motor just behind the seats which was belted directly to the rear differential (direct-drive). He had also gotten hold of an SCR motor controller http://www.bakersfieldads.net/Quailwood-/New-8-msc-D1939-medium-sized-standa rd-power-scr-to-94.jpg SCRs have a limit on how high a frequency they can operate. He offered me a ride (how I got my long legs in the small sedan I do not remember), but when the PWM controller chopped the current, it was quite audible (I mean we are talking loud here). As the current groaned its way through the motor windings that were just behind our heads, the EV performed fine. If you (like the driver) ignored the SCR sound, it was a fine ride. But what about before power semiconductors? If you bring up the video in the (above) post, and go 1 min & 15 secs into it, it shows the driver pushing down on what seems to be a lever that moves a wiper across thick large gauge solid wires wrapped around an insulator. I will assume that was to be a rheostat. I found an image that is similar http://i.ebayimg.com/t/Biddle-Precision-20-Amp-Laboratory-Rheostat-Lubri-Tac t-411D200-0-94-Ohms-/00/s/NDgwWDY0MA==/$T2eC16hHJF8E9nnC9c+PBQUNluTcMw~~60_3 5.JPG Considering the TV crew built that electrathon-ish EV on their own, I think they did a pretty good job. BTW: There were also early EVs that used multiple taps off the battery pack to adjust the acceleration. That could be a jerky ride between jumps, either up or down in voltage. {brucedp.150m.com} -- http://www.fastmail.fm - A fast, anti-spam email service. _______________________________________________ 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) -------------- next part -------------- An HTML attachment was scrubbed... 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