Hi David,
That is a good description of the two. However, the only thing I would take exception to would the last comment on the DC drive. Yes, AC motors have a far better torque curve over the RPM range and the controller can regulate the power/frequency to the motor to keep it operating at its best. But keep in mind that unless you are planning to eliminate the (manual) transmission, you will have gears to help keep the motor in a good operating RPM range. Very few conversions go direct drive (AC or DC) mainly because of the RPM range of the motors. While an AC motor can give you a better torque curve over a greater RPM range, the torque curve on the typical DC motor is sufficient enough to provide excellent usability, particularly at lower RPM. I guess what I am trying to say is that while I agree with your analysis of DC vs AC, I wouldn't dismiss a properly designed DC motor conversion as lack-luster. I can think of one particular black EV with DC motor(s) and no tranny that can keep you in your seat all the way down the road. Shawn _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David, FloridaAME Sent: Monday, March 17, 2008 7:19 PM To: listserv@floridaeaa.org Subject: [FLEAA] Regen I am trying to pick parts to plan a conversion and regen possibilities are on my mind also. I have started with the dynamics of the moving car and studied my commute to work and back home. My trip is about 7 miles each way, speeds are 35-45 MPH, and has 18 stops/starts. About 20% of the trip power goes to acceleration and will be wasted later with mechanical brakes. The series wound DC traction motor has a lot of toque and power in a low cost package. The armature current flow through heavy field wires in the series configuration. The high current for high toque makes it efficient making torque. Unfortunately the fields design needs high armature current for the proper magnetic field strength to make it be a generator and do regenerative braking and generator action is just not part of the motors operation. If you want to add a bunch of complexity, a bunch or relays to separate the armature and field and power the field with low voltage you can make it work, but the complexity outweighs the benefits. The AC motors like other DC motor configurations have no problems with regeneration. The big problem is the AC motor and controller cost about 3 times more and usually run on higher batter voltages (more batteries, still more cost and safety issues). >From my experience with industrial motors Regen will only harvest about 50% of the available energy. The cost of AC motors exceeds the losses in efficiency. I am personally still leaning towards AC however. Not because of regen but because the torque the motor produces is relatively constant regardless or speed. The series DC motor has lots of low speed torque that drops off with speed and I think that will end up with a lack luster drive. Now the problem is how to manage the high cost. Nothing worthwhile is easy. David Kerzel
_______________________________________________ Florida EAA mailing list listserv@floridaeaa.org http://www.floridaeaa.org
