[ausev] A little confused about motors....

[Erik]

To make things a little more confusing, all of the below is true of series
DC motors, but there is a wide world of motors out there. Series DC are the
most common to work with for conversions though for their availability and
strong low speed torque.

Series DC motors can regenerate, especially when built with interpoles, but
it's mostly a function of the motor controller. The Zapi motor controllers
will regen with a series motor, and the Zillas have built in speed control
and stalled motor monitoring so you don't burn your comm up holding your
place on a hill.

Higher RPM is a function of price and function, since the brushes limit
series DC motors to a certain speed, they don't need the extra cost of
balancing for high RPM operation.

Since AC motors require a lot of tuning and programming to make them work
anyways, all of the extra bells and whistles are added for relatively little
money since fancy mircos are already used for the motor control.

Erik


On Wed, May 28, 2008 at 9:19 PM, Rob <rob at zehicle.com> wrote:

> Except for price, AC motors have several advantages over DC:
> 1) regenerative braking (can add 10% to range)
> 2) simpler motor
> 3) built-in RPM monitoring
> 4) better stall & torque control
> 5) higher RPM capabilities
> 6) easy to reverse (no need for transmission or x-wiring)
>
> Of course, price is generally a factor for a conversion :P
>
> -----Original Message-----
> From: ausev-bounces at austinev.org [mailto:ausev-bounces at austinev.org] On
>  Behalf Of Gil Dawson
> Sent: Wednesday, May 28, 2008 8:56 PM
> To: AustinEV News Announcements and General Discussion
> Subject: Re: [ausev] A little confused about motors....
>
>
> At 6:41 P -0600 5/28/08, evehicle4me at hischopsticks.org wrote:
> >  Doesn't DC (from a battery) need to be converted to AC to be able
> >to power an AC motor?
>
> Yes.  That's one of the functions of the controller.  Think
> oscillator and power amplifier.  Then make the power amplifier REALLY
> BIG and connect it to the motor instead of speakers.  When you
> control the oscillator, the wheels follow.
>
> >Is there a significant loss in the process?
>
> Yes, and there's significant compensation.  AC motors are simpler (no
> brushes.)  A sophisiticated controller can control them more
> precisely.  I wonder whether a DC motor can even do regen?  I guess
> it could.  I'd be interested to know whether regen is a typical
> feature of commercially-made DC motor controllers.
>
> GM and Toyota both chose AC in their commercial products, the RAV4EV,
> the Chevy S-10E and the EV1.  The Prius uses two
> separately-controlled AC motors.  The big guys must like
> sophisticated controllers.
>
> --Gil
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