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Variac And Isolation Transformer Questions Addressed, With Safety Advice.
🕑 Added 2022-08-16 23:08:53 +0000 UTCSome commonly asked questions about Variac's and Isolation Transformers. Also: safety advice, and the differences between these and other transformers. Enjoy!
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Comments
Ken Hammond
I have a variac with the power switch, fuse and voltage meter already built-in. Would it work to have the current-limiting bulbs off the tap of the variac, before the isolation transformer? And what do you do with the outlet's ground wire on the isolated side? Wouldn't there be problem connecting it to the ground on the line side?
Butch - KAØWWT
I recently bought a Variac based on your videos. Can I just dry brush the variable voltage run with a brush, or should I just leave it alone and not mess with it at all? It needs to be reconditioned as someone dropped it and bent the outside of it. Everything inside is fine visually. I have not smoke tested it yet......but I will be. ; - )
Lily Finley
It's also worth noting, an isolation transformer can make a GFCI outlet / breaker unable to detect ground faults downstream of the transformer.
Lily Finley
One option to reduce errors is to use a DPDT switch, and use the second pole to switch an indicator light. That indicator could be a separate device or integrated with the switch.
John Moorhead
An alternative to removing the ground pin on the plug is to add a switch on the front panel of the AC line isolation device that either connects the ground from the line to the ground pin on the output socket(s) or isolates the ground on those sockets from the line ground. This gives you the flexibility of configuring it for use in different situations. For example, on my Hammond 178 series torroidal isolation transformer unit, I've added a front panel switch to ground the output sockets to the line ground or isolate them. Adding the switch gives you flexibility when using the device, but it also adds a risk component in that if you assume the switch is in isolate mode but is actually in the other position (or vice verca), you could create a dangerous situation. Caution - modify at your own risk; always check the ground isolation switch position before applying power, and if you do not know exactly how to make this mod and when (and when not) to implement it, DON'T DO IT!
