Seth Murray wrote: > > hehe, guess I don't know too much about motors now do I?? =) here's a > dumb question - if our motor here is making all this back EMF, if we > are coasting down a hill and keep on winding the motor up and up and up > until the BEMF exceeds the input voltage, would we not have regen? My > understanding was that series motors are tricky to do regen with. Why > would that be, if we have this apparently straightforward EMF thing > going on? Thanks for the info. > > "Us racers swear at them..." someday, Rich, I will give you a run for > your money (or a new PFC) =) > > Seth > > On Saturday, September 28, 2002, at 01:12 PM, Rich Rudman wrote: > > > Seth Murray wrote: > >> > >> Peter VanDerWal wrote: > >> > >>> the resistance through the brushes on a moving comutator is different > >>> than on a stationary one > >> > >> I have been wondering about this. Lets say I am driving in second > >> gear. When I first start my EV moving, the motor wants lots of amps. > >> Once it gets up to 4,000 rpms or so, the motor seems to have a limit > >> on > >> its current draw, even if I put my foot on the floor (current well > >> under the current my batteries and controller can deliver). As soon > >> as > >> I shift into 3rd, though, the motor will take all the current my poor > >> batteries and controller dish out. The only thing I could thing of > >> was > >> that the resistance through the motor must change depending on rpms, > >> which because of Ohm's law would allow the motor greater current at > >> lower speeds. I know there are other factors involved, but do I have > >> any clue of what's going on? =) > >> > >> Seth > >> > >> -- > >> QUESTION INTERNAL COMBUSTION > >> > >> My electric truck page, with lots of photos and a 25 page conversion > >> journal. Check it out! > >> http://www.wpi.edu/~sethm (NO MORE POPUPS!!) > >> > >> My EV Album page > >> http://www.austinev.org/evalbum/387.html > > > > HOooooH ha ha HHHHEEEE! Yea rather obvious is the BACK EMF of the > > motor. > > As it spins up it becomes a generator, you need to over come this with > > more volts or your motor will spin up to a certain speed and then wind > > out no futrther!!!! > > Basic V/F ratio. volts to Frequency or RPM same thing. > > All motors have rpm and torque curves. You are just seeing them . > > Us racers swear at them and try to manipulate them to our best uses. > > > > Check the motor curves from Advanced DC and from Rod at EVparts, and > > Ken > > Koch at KTA. > > > > > > -- > > Rich Rudman > > Manzanita Micro > > www.manzanitamicro.com > > 1-360-297-7383,Cell 1-360-620-6266 If you excited the field of the Series wound motor while spining at some un Godly speed your FACE would cross the Stearing wheel plane!!! It's VERY eary to get a series wound to regen, but because it's a Squared funtion it's a real pain in the Arse to control it. In AcDC motors with a seprate field post you can run them as SepEX motors and then the control issuse is basic. You just need a 1000 amp 2 volt source and the control gear to make it happen. This will be the control strategy on the Project 8 Dyno that is getting closer to existing. The Real issue is the brush timing. This makes efforts at this hard because you need a optimal brush lead advace for motoring and just the opsite for brake regen. A non interpoled motor will suffer, unless you dynamicly move the brushes. If you get smart you have the field windings rewound for less current and more voltage, and then you have a Sepex motor and controller. That HAS to have a custom field controller. You will loose the series wound chariteristics of massive torque at low to Stalled RPM, and NO field controller. Sepex is the New Old thing in Ev control right now. But you have to have the right motor and controller matched to each other. It's a drive system. Old Series wound and a DC chopper of just about any sort works and works well, but Regen is not free. After you get about 1/2 way there with contactors and H bridge field controllers and the main 600 amp aramture controller, and the micro code to get all this to happen, you are over %90 the way to AC induction control. That's why AC induction is coming out of nowhere in the high end fork truck and materials handling markets. As it should here in the EV drive world.
-- Rich Rudman Manzanita Micro www.manzanitamicro.com 1-360-297-7383,Cell 1-360-620-6266
