Re: Dimmer as a Variac.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Ed,

At 07:33 AM 7/7/2001 -0700, you wrote:
>Tesla list wrote:
>> 
>> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>> 
>> Hi All,
>> 
>> Today I got a Leviton No. 6681 600 watt dimmer switch at the hardware
>> store.  It cost me about $7.  I imagine these are available everywhere at
>> least in the USA.  I pulled the back cover off to expose the electronics:
>> 
>> http://hot-streamer-dot-com/temp/P7060004.jpg
>> 
>> Wow!  They sure are cheap!! :-))  All hand tack soldered.  Many
>> opportunities for shorting and such...
>> 
>> The main power electronic device does not have heat sink compound under it.
>>  I think drilling out the rivet and adding a little thermal grease will
>> increase it's short term power handling about 200%!
>> 
>> Not enough room inside to add internal MOVs but a little thermal grease and
>> some "adjustment" of the guts should help them to survive considerably.
>> 
>> I am thinking that MOVs and a good line filter will complete the poor man's
>> variac and I can do a little testing to see if the idea is worth while.
>> Still have to check what the output wave forms look like and see how that
>> will affect the rest of the coil...
>> 
>> Stay tuned...
>> 
>> Cheers,
>> 
>>         Terry
>
>	I predict you are going to be very disappointed!  The performance of an
>SCR/TRIAC dimmer is very different with an inductive load, which your TC
>primary circuit will probably be at the frequencies which commutate the
>SCR.  Hope I'm wrong.
>
>Ed
>

You bet!  Running that little TO-220 thing into a highly reactive load (but
my coils are PFC corrected) with "strange things" being reflected backwards
from the spark gaps and all will be a "challenge" for the dimmer!! :-))
There is also the radiated and conducted in noise and such that may affect
their operation.  However, given the commodity pricing of the things, there
is plenty of room for added circuits if that will allow them to work.
Right now I am just exploring the possibility without any great confidence
that they can be made to work well.  However, if they could be made to
work, it would be cool!

Cheers,

	Terry