Re: nubie questions

[Colin Dedman <cjd121@rsphy1.anu.edu.au>]

Jay Lopes wrote:
> 
> Bill Dube wrote:
> >       How deep are your pockets? DC drives are inexpensive and powerful.
> >Commercially available AC drives (brushless DC drives included) are very
> >expensive and wimpy.
> 
> Bill is half right (as usual, and he has AC envy), AC drives are expensive
> but they are sure as hell not wimpy.  What is your budget like, if you
> don't mind me asking?
> 


On the basis of "bang for buck" nothing beats DC drives - Bill is right
about that. It may be a little rash, though, to broadly label AC drives
as "wimpy". 

One of the advantages of playing with very small EV's (like I do) is
that high-performance AC drives, or BDC motors, become vaguely
affordable, albeit they are still vastly more expensive than a brush
motor. I gotta tell you, Bill, that for the smaller motors that I play
with (up to 3HP) the better BDC motors will clean blow the pants off a
poor old brush motor. You want some specs to back that up? Just ask.   

E-car enthusiasts are kinda stuck in the stone age though, because
really large state-of-art AC motors (and controllers) are either too
expensive to buy, or nobody makes them.  The dinosaurs ruled for many
millions of years, and DC brush motors will be around for a while yet
simply because they are cheap, not because higher performance AC (or
BDC) motors can't be built. 

It should be noted, too, that Bill's definition of "wimpy" probably
means that it cannot be overloaded by a factor of 20 (probably at 20%
efficiency) for 1/4 of a mile. That's fair enough for Bill's
requirements, but far less relevant for normal use in a normal
E-vehicle. I'm not knocking the good old DC brush motor though, they do
a fairly good job at a very good price, and are forgiving of gross
overload.

Best regards,

Colin Dedman