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Vincent,
Did you happen to change fuse types at some point. I would think you
would want a slow blow type. Also, a long shot on this, but make sure
the fuse connection is tight and clean and that the clamping or holding
is not loose. A loose connection might add heat to the fuse and perhaps
blow the fuse sooner. Not certain but just a thought.
I doubt that your supply mains voltage has gone up but in some weird
cases the balance of the two legs of 240VAC can change (neutral loose
connection or open neutral in your box or house feed) making the 240
unbalanced with maybe 140 and 100VAC instead a balanced 120 and 120 VAC.
That is a unusual but it has happened. If your mains was higher than
120 VAC the variac could take it even higher and you would draw
excessive current. Are you getting longer arc length than in normal
years in the past, just before the fuse blows?
Any leaking filter capacitors or line filter failure starting if wired
after (downstream)
the variac? Let us know what you find. Best of luck with this.
And if you ever run 4 12/30's NST I think you will need a higher
current rated variac. Variacs can take higher currents than their
ratings for a short period of time.
Terry Leonard
On 11/24/2015 4:46 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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