Voltage regulator

[Bill the arcstarter]

It was written:

>>Using PWM control is better yet, as it does NOT reduce the peak
>>voltage/torque at all - it just modulates it. PWM control on a DC 
>>type motor reduces speed without APPRECIABLY reducing torque.
>
>To claim that there is not enough inductance in the motor windings to
>smooth out the highs and lows of the PWM voltage notches is living in
>dreamland or a sign of having ingested too much egg-nog!!

Actually you can (and will) instantaneously change the voltage across an 
inductor (motor winding) w/o an instantaneous change in the current.  
Nothing in physics says otherwise.

I suppose the question is one of *what* damages the motor - rapid force 
oscillations (caused by rapid changes in current - something which is 
limited/prevented by the self-inductance of the windings) or some form 
of (?) dielectric breakdown across the windings caused by rapid voltage 
fluctuations... ?

The big boys do use specially insulated magnet wire on the larger (1-10 
hp) motors designed specifically for use with chopper drives.  I'm not 
sure if a smaller motor (like a fuel pump) would care one way or the 
other.

If you build such a chopper - be sure to include a flyback or snubber 
circuit to prevent your fet/transistor from going POOF due to the 
inductive kickback. :-)

-Bill
(building a 10000 watt phase controlled SCR driver for my stick welder)
Wanna know how to turn OFF an SCR?  See my page:
http://www.geocities.com/CapeCanaveral/Hangar/6160/hvtank/hvtank.html


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