I had 2 12kv 60ma NST that were blowing 20amp fuses in my variac. I can now run 3 12KV 60ma NST because I added 10 50uf 370V ac caps for pfc. I put a amp meter gauge on the incoming 120v feed. Then Ikept adding he air conditioning run caps till I got what I wanted the lowest current draw which was around 9 caps, used 10 cause it was a even number. But I can run it without blowing fuses or tripping circuit breakers again.
John Cooper
Sent from my Samsung GALAXY S5™, a Cricket 4G LTE smartphone
-------- Original message --------
From: David Speck <Dave@xxxxxxxxxxxxxxxx>
Date: 11/24/2015 21:58 (GMT-06:00)
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Recent variac problem.
Vincent,
What is the rating of the fuses you are using? 10 amps?
Are they slow blow or fast blow fuses?
Many old-school name brand variable autotransformers (Variac, Powerstat)
can handle double their rated nameplate current ratings for short runs
of 30 - 60 seconds without being damaged. Can't say the same for some
of the cheap Asian imports, though.
A Variac is not the part of the circuit that provides current limiting.
That is established by the NSTs themselves.
If you want to run 4 NSTs simultaneously, you will need a Variac big
enough to provide the all current they require.
Adding power factor correction capacitors (PFC) to the transformer input
may help manage their current drain.
Dave
On 11/24/2015 7:46 PM, Vincent D'Amore wrote:
> Hi All
>
> Recently I've been running my coil controlled by a 10amp variac. I'm running two parallels 12/30 franceformer neons sign transformers and have been running this way for several years but as of late I keep blowing fuses on the variac about every 4th run. I'm not sure if or what has weakened over time. I would like to run my coil with a much larger power supply but that obviously won't go over well with my 10amp variac and I certainly don't want to move forward until I know the weakest point. Any suggestions? Also if I do go with a larger supply I'm thinking of 4 12/30's in parallel but don't know what to do for current limiting. Larger variac? Something else? Thanks for any advice.
>
> Vincent
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