I've been lurking here on your forum for some time now. I've been looking at EV possibilities for the last... <drum role/> week.

One of the first questions I have in developing my project is exploring considerations tractor solutions.

I hear that AC solutions have the following characteristics: (FYI corrections / clarifications welcome)

- low end torque (as in below 1/3 of the motors nominal RPM rating) is poor.
- the rotor phase must slip behind the voltage curve to generate torque, the result is a degraded power factor resulting in systemic inefficiencies.
- DSP type solutions required for motor control.

I became interested in AC Synchronous type solutions, ideally the DC-excited solutions, of which an standard alternator is quite similar.

Look at these Permanent Magnet Synchronous Motors (PMSM): http://www.boschrexroth.com/dcc/Vornavigation/Vornavi.cfm?Language=EN&VHist=g97568,g96068&PageID=p146808

Simply contemplating the engineering solution I believe it addresses the first two issues in the list regarding AC solutions above.

Economics aside, imagine an A4 chassis with one of the 47.6 Kw MSS142F-0700 powering each wheel at a 5 to 1 ratio. The site is wrong in that Max RPM is 10K rather then 28K, FYI.

With 225/55 R17's (84 inches circumference), that means at nominal RPM (7K) the car would cruise at a cool 111 MPG with 255 HP and 958 ft of torque.

I'll have to work out the power source for this... glass-mat batteries maybe.

On a side note, the nominal specifications are at 540V DC on the inverter bus. The motors are rated to 750V max... The is running such high voltage a serious problem, even in a well designed EV solution? The motors rated current at 7K is 68 x 4 Amps and the system need some multiple, n, of 45 12V cells to obtain 540V. The question then becomes how many sets of 45 cells to wire in parallel. I clearly need to examine the power source requirements for this solution _way_ more thoroughly.

Any other considerations?

Thanks in advance for any comments.