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Registered Member #621
Joined: Sun Apr 01 2007, 12:37AM
Location:
Posts: 119
Is it safe to use a 120v mains rated rheostat (regular light dimmer or motor controller type of the rated draw) on the input side of my 4kV NST or will it create problems? I'd like to be able to infinitely adjust thevoltage of my cap bank on the NST secondary. Thanks.
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
What your looking for is a Variac to control input voltage, not a rheostat to limit current. Light dimmers are not usually rheostats anymore, but triac devices that control peak voltage. It probably wouldn't be a good idea to use on with a transformer or other inductive load due to the severe waveform deformation, although I could be wrong.
A motor controller may be a modified light dimmer circuit, or an actual rheostat (probably not because they are very inefficient), neither of which will help you.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I use a Variac. The only thing I would like to add is make sure it is fused. This way you blow the fuse and not your breaker or worse your wall wiring.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
If you can't tell if your rig has a fuse you probaly shouldn't be working with high voltages. Anyway, how much does it cost to include a fuse and how much does a new variac cost?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
As a side note; Put the fuse AFTER the variac to protect the wiper/brush/carbon whatever.
Remember that a Variac is a Variable TRANSFORMER so when set for example to 1/10th voltage output, the output current can be up to 10 times the input current.
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What makes a good rheostat for an NST?
