Re: Can a light dimmer substitute for a variac when setting up a tesla cilo?

• To: tesla-at-pupman-dot-com
• Subject: Re: Can a light dimmer substitute for a variac when setting up a tesla cilo?
• From: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net> (by way of Terry Fritz <twf-at-verinet-dot-com>)
• Date: Tue, 02 Mar 1999 16:57:33 -0700
• Approved: twf-at-verinet-dot-com

Hello Dave,

>Original Poster: "David Hosking" <davidhosking-at-bigpond-dot-com>
>I have read the posts on changing motor speed with a light dimmer and
was
>wondering if you could use a dimmer to replace the variac supplying the
NST's
>to operate the tesla coil at low power for setting up.
>
>Also I am able to buy a 500va variac and my coil is using 2x15kv 60ma
NSTs
>Could I use this variac for short runs with a good cool-down after?
>
>If so,  how long should my maximum run time be?


I wouldnīt go for a triac NST "dimmer". Triacs donīt like inductive
loads and they are RF spike sensitive. Plus, if the triac fails (short
circuits) you would most probably feed the full current to your
NST. Not something you would like to have in an emergency
case. On Superiorīs website I found a note about their variacs,
saying that they can be overloaded by 400%. The duty cycle is
rather low (around 10min/hr), but on a whim, it might work for
you You would overload your 500va variac by 360%. I guess
it depends on how much you would have to pay for this variac.
A 1-2kVA variac shouldnīt be that hard to find (swap meet)
second hand. I think this might be the safer and cheaper way
to go.


Coiler greets from germany,
Reinhard

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