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Re: Triac-dimmers in TC's



In a message dated 2/27/99 4:21:16 AM Central Standard Time, tesla-at-pupman-dot-com
writes:
  Gary

  I have used triac control for AC/DC motors and induction (permanent split
capacitor) motors.  The schematic is in T.C.B.A. News vol. 17, #1.
  It uses an SK-3659 15 amp 400 volt triac in a simple "lamp dimmer type"
circuit with a snubber consisting of a 100 ohm resistor and .22 uF capacitor
in series accross the triac.  The output is fed through a conventional E.M.I.
filter to the motor.
  There were never any run away problems or glitches in operation even running
in a wooden enclosure.
  For a long time this controlled a 1/3 H.P. induction motor in a 10 kW setup
without flaw.  The drawbacks I had were with larger motors that were heavily
loaded pulling too much current at start up blowing the triac.  Also I had a
direct strike to the motor once and it took out the E.M.I. filter with triac.
The good news is the triacs are cheap to replace.  I believe I bought the
traics thru All electronics mail order and the 20 amp Cornell-Dublier filters
from MECI mail order.

Kevin E.


> Has anyone had experience using a solid-state off-the-shelf lamp dimmer
>  to control the speed of a motor in a Tesla Coil?  I'm currently using a
>  variac on my gap's vacuum cleaner motor, but I thought I'd save some
>  space and just use a solid-state dimmer.  The motor is an AC/DC
>  "universal" type.  I'm just wondering if the voltage spikes and
>  interference would either toast the semiconductors or confuse the control
>  circuit.  Please don't speculate and suggest using a filter unless you
>  know, from experience, that it won't work without it.
>  
>  Thanks, Gary Lau
>  Waltham, MA USA
>  
>  
>  
>  
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