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Re: [TCML] Variac
On 05/06/2013 08:39 AM, Tim Flood wrote:
Looking for a variable transformer for my new find, a 14,400/120V potential transformer. I have have checked eBay.
Does anyone have a variac for sale, at least 30 amps?
Hi Tim, one thing to keep in mind about variacs is that most domestic
versions are rated for continuous duty. This means that a 30A variac is
rated to control 30A 24/7.
If you want to run them at a higher current than they are rated for, you
can do this, provided that you limit the duty cycle of the variac (the
limiting factor is the amount of heat that builds up). The
manufacturers actually plan for this, and provide a duty cycle chart for
As an example, here is the duty cycle chart for GE Volt-Pac variacs
(other manufacturer use a similar curve):
As you can see, you can run a variac at double the rated current,
provided that you limit the duration to less than ten minutes. In Tesla
coiling, this usually isn't a problem, because we generally limit the
run time to less than a minute or two (I personally use a 25A, 240V
variac at 60A with no problems whatsoever, and actually built the power
supply with this in mind).
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