Subject: Variable speed, constant torque

From: [email-masked]
Date: Sun, 28 May 95 01:09:16 EST

-=> Quoting Internet: [email-masked] to ** All ** <=-

 IS> One problem with this is that just using a Variac for
 IS> speed control will yield very poor torque at low speeds.
 IS> What is needed is a thyrister (SCR) controller similar to
 IS> what is in a typical variable speed portable power tool
 IS> but on a larger scale.

Actually the Variac is better than the SCR/Triac controler even
at low speeds.  The electronic controlers work by delaying turn
on for a portion of the cycle.  At slow speeds, this means that
only a small potion of th sinewave will be presented to
the motor, with a large off period betweenpulses. This leads to
cogging of the motor. By contrast, the variac provides true
sinusoidal ac, reduced in amplitude, at all speeds.
Regards,
Brad Chaucer

... I'm a DOS user until WINDOWS freezes over!
___ Blue Wave/QWK v2.12

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From: [email-masked] (Daryl Bender)
Date: 29 May 1995 21:10:43 GMT

> ... I'm a DOS user until WINDOWS freezes over!

What happens if you put your SCR/Triac controler (with FET switchers)
output into an rectifier with filtering?!

-- 
Working but not speaking for BNR