John,
Depending on the size and manufacturer of the variac, it is may very well be the inrush of initial power up of the variac itself that is tripping your breaker. I'm had much issues with this with variacs of 15 amps or more rating. The real "poor boy's: way to address this issue is to run your system via an appropriate guage 100 ft. extension cord. The added relatively small impedance of the extension cord itself is often enough to squelch the instantaneous current rise at power up enough to correct this problem.
David
On Thursday, September 3, 2015 9:20 PM, wt5y <wt5y@xxxxxxxxx> wrote:
So I put dmm in amp mode, switch probe leads to 10 amps plug, current Xformers over the cord or just the hot wire? And if it is running 25 amps I would see 2.5 amps on my meter?
Sent from my Samsung GALAXY S5™, a Cricket 4G LTE smartphone
-------- Original message --------
From: David Speck <Dave@xxxxxxxxxxxxxxxx>
Date: 09/02/2015 23:13 (GMT-06:00)
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Power factor correction
John,
Check out eBay for a current transformer. A 50:5 unit will multiply
your DMM readings by factor of 10. They should be available for under
$20 with some diligent looking.
Something like the following would work. (no connection to seller.)
http://www.ebay.com/itm/130895906892
Just be careful to never put current through the transformer (CT)
without having a load, like your DMM on its amperes setting, across the
CT terminals. When unloaded, a CT tries to put out infinite voltage
which may break down its internal windings.
Then, you can investigate which arrangement of PFC caps works best for you.
Dave
-----------------------------
I'm at the point I need to add some motor run caps, I'm thinking the
same that go on your ac units in the 40-50uf 330-440v variety unless
someone has a better suggestion. Looks like I will need around 150uf
per transformer I have 3 12/60 NST. Biggest question is do I run all 9
parallel or run about 3 strings of 3 to each? Would before or after the
EMI filters make a difference. Blowing 20 amp fuses on variac, don't
have a clamp meter and my dmm is only good to 10 amps inline. I was
going to add some and then start measuring the current? John Cooper
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