Can a short on a high-voltage secondary trip your house's circuit breaker?

andrewRneumann

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Here's one thing I don't understand, though. I thought that on the secondary side of a transformer, the vintage truly is floating, and it really only wants to flow from one secondary lead to the other, or to the center tap, if it's rectified. So why would touching a single lead even "bite" me at all? Where's the reference voltage that says "your finger is at a much lower voltage than the wire, therefore, the wire's voltage will flow through your finger to reach ground". Why is it not just that nothing happens, since your finger is now referenced to the secondary voltage?

Once you ground the HT CT to the chassis it is no longer floating. Current goes through you, out your shoes, through ground, back up the safety ground, into the chassis and finally into the HT secondary. That’s if you aren’t touching the chassis or other HT lead with your other hand… and this is why rubber shoes and mat are suggested.

In the case of a transformer not grounded to anything, you are correct. Nothing happens unless you touch 2 leads simultaneously. I think this is what’s happening with the fatal fractal art—the body is making the connection between two HT leads.
 

dsutton24

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Here's one thing I don't understand, though. I thought that on the secondary side of a transformer, the voltage truly is floating, and it really only wants to flow from one secondary lead to the other, or to the center tap, if it's rectified. So why would touching a single lead even "bite" me at all? Where's the reference voltage that says "your finger is at a much lower voltage than the wire, therefore, the wire's voltage will flow through your finger to reach ground". Why is it not just that nothing happens, since your finger is now referenced to the secondary voltage?

This is where theory and reality diverge. In other words, "A little learning is a dangerous thing." Thank you, A. Pope.

You don't know that the secondary is "truly floating", as you say, nor do you know what potential either leg of an unreferenced transformer is sitting at. You don't know what potential your finger is at. Microwave oven transformers have secondary voltages in excess of 2,000 volts. Things get spooky at high voltage.

And for god's sake, get the idea out of your heads that ground is necessary for anything bad to happen. There's nothing magic about a ground connection, it's just a reference.

If you young folks don't believe me, ask anyone who ever tangled with a live chassis on an old fashioned color t.v. or oscilloscope. Those things would bite the hell out of you whether any part of your anatomy was grounded or not.

And when you get into the world of r.f. well, all bets are off.

Seriously, folks, some of you are heading for headstones that read, "He was right, but he's still dead."
 

Blrfl

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You don't know that the secondary is "truly floating", as you say, nor do you know what potential either leg of an unreferenced transformer is sitting at. ... And for god's sake, get the idea out of your heads that ground is necessary for anything bad to happen. There's nothing magic about a ground connection, it's just a reference.

The key words are potential and reference. Using your body to complete a circuit between two points where the voltages are 425 and 300 is no different than grabbing 125V headed for earth ground. The 425V point will see the 300V point as a place with less potential and, therefore, a reference. Current will flow that way and it's gonna hurt.
 

tubeswell

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Can a short on a high-voltage secondary trip your house's circuit breaker?​


Depends on the sensitivity rating of your RCD, and whether you had the wrong sized mains fuse/foil wrap/paperclip etc in your mains fuse holder. A load is still a load, and a bigger than usual load is still a bigger than usual load.
 

2L man

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If amp own fuse does not burn eventually house curcuit breaker trip the mains Off.

Generally transfirmer secondary current leak do not trip "30mA ground current leak C/B" as long as mains stay isolated when transformer primary insulation function.
 




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