Re: ...another newbie question (Variac fuse blowing)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

Dennis -

We need more information on your setup. Under normal operating conditions, a
15/60 NST won't draw enough current to blow a 20A fuse.
1. Is the variac supplying power to the NST only?
2. Are the fuses you are using of the fast or slow-blow type?
3. Does the fuse blow as soon as power is applied to the variac, or only
when the coil is operating and the variac is turned up to maximum power?
4. Is the variac wired to provide 0-120 volts out, or 0-140 volts out?
5. Is your NST a high power factor type, or a normal power factor type?
6. Where is the fuse located? In the input circuit to the variac, or on the
output side of the variac?
7. What is the current rating of the variac? Large variacs (20 amp or
larger) will have large inrush current as soon as power is applied. This can
cause a fast-blow fuse to open, if the fuse is located in the variac's input
circuit.
8. Do you always power up the variac when its turned down to minimum output
voltage?
9. Does your system use a static spark gap, or a rotary spark gap?
10. What is the value of your tank capacitor?

These answers should help in diagnosing your fuse problems.

Regards,
Scott Hanson

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, November 27, 2005 5:12 PM
Subject: ...another newbie question


> Original poster: otmaskin5@xxxxxxx
>
> Thanks for all the advice on the hazards of indoor coil
> operation.  After hearing from you guys, man am I glad I asked.
>
> I've got another technical question if anyone would care to weigh
> in.  My 4" coil is powered by a 15/60 NST.  It keeps blowing the 20
> amp fuse in my variac.  I think this means the coil needs PFC.  I'm
> pretty sure I know what kind of caps would be right, but I'm having
> trouble determining the proper way (where & how) to hook them up.
> Could one of you help me out this info?
>
> Thanks.  Dennis Hopkinton MA
>
>