At 10:29 PM 3/11/02 +0000, you wrote:

>The other problem is that I don't think AC induction motors do very well
>having their speed controlled only by voltage reduction.  Without
>reducing the AC frequency as well, they are forced to run in a high-slip..

Yup, that's why "phase control" type speed controls (as you can get off
the shelf at Home Despot) only really work with motor loads such as fans-
where reducing the motor torque reduces the speed with little danger of
stalling- IOW, the load is mostly drag with little stick-slip friction.

If you want to vary the speed and maintain torque, you need to change the
frequency which is non-trivial.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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