Re: Variac vs. Fan speed control

Subject:   Re: Variac vs. Fan speed control
  Date:    Thu, 24 Apr 1997 15:22:11 +0500
  From:    "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
    To:    Tesla List <tesla-at-pupman-dot-com>

On Mon, 21 Apr 1997 09:29:22 -0600 (MDT) Chip Atkinson
<chip-at-XiG-dot-com> wrote;

> > They are totally unsuitable for 
> > voltage control, could be use to vary the speed of a SMALL ac motor
> > running a rotary gap but not the low side of a drive transformer.
> Not quite true.  They are totally unsuitable for the rotary gap too.
> I tried this a long time ago.  The controller was an actual motor
> controller (not a light dimmer) that I got at an electric motor place.
> The problem is that once the coil starts firing, the controller loses
> its mind and the motor goes full speed.  Turn off the coil and the motor
> controller returns to normal.
Hay Chip, ever hear of a Faraday shield? Seriously, Chip I currently 
use phase shift light dimmers to control my rotory spark gaps {I use 
universal motors} and I have no problems BUT I totaly enclose the 
dimmers in a grounded metal box. Apparently what happened in your 
case is the triac was picking up some of the radiated R.F and being 
driven into continous conduction, try it again but this time enclose 
the control in a grounded metal enclosure.


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