Re: why are EV DC propulsion motors all series wound?

[Robert McDonald <s348607@student.uq.edu.au>]

jim leuba wrote:
> 
> Rob:
> 
> The newer industrial 3 phase AC controllers are coming down in price
> rapidly.  Most of them are running internally on a 300 volt DC bus
> (rectified 220VAC).  Why not use one of these (with a 200-300 VDC
> battery pack) and a plain old 3 phase squirrel cage motor.  These
> digital controllers have DC boost (increases low end torque) and can
> also run a 60 hz motor at 120 (or more) hertz.  A setup like this might
> be able to eliminate the transmission.  The name brand controllers are
> almost bullet proof (low maintenance).

Sure, this would work fine!!!  But how much are these controllers?  And
what is their efficiency?  Are they vector controlled or v/f type
controllers?  

I am planning to use a squirrel cage motor with my home made controller,
this combination should easily be price competitive with an ADC
9"/curtis combo (in Australia).  The other thing which can easily be
done is to rewire the standard 4 coils per phase (4 pole motor) in
parallel rather than series, this means that the rated hp is produced at
a much lower voltage but the insulation is still good for high voltages,
thus making it extremely easy to get much larger power ratings when the
motor is run at its original voltage!  This means that a 10kW motor can
be run at 40kW, just by reconfiguring the coils.

I just remembered you are in the motor repair business so you were
probably aware of this already...

I'd really like to hear details of specific off-the-shelf AC
controllers, I haven't had much luck finding someone knowledgable in
this area, who understands the requirements (or is interested in finding
out) for EV applications...

Cheers,
Rob.