Re:Why we ground electrical systems (2015)
by Gibbon1 on Saturday August 03, 2019 @02:52AM
(#20599056)
> So what's up with that?
Usually 50 VAC means the ground is open.
A thing about most ordinary transformers[1] is they wrap the primary and secondary together. Fast, cheap, and more efficient. The result is there is a large amount of capacitive coupling between the primary and secondary. Since one side of the secondary is grounded it's like connecting 1000-5000pf between hot and chassis ground. If chassis isn't grounded then it floats at 60VAC.
[1] For transformers with more isolation they wrap the primary and secondary on top of each other. Less capacitance that way. Medical grade transformers have physically separate windings.
Usually 50 VAC means the ground is open.
A thing about most ordinary transformers[1] is they wrap the primary and secondary together. Fast, cheap, and more efficient. The result is there is a large amount of capacitive coupling between the primary and secondary. Since one side of the secondary is grounded it's like connecting 1000-5000pf between hot and chassis ground. If chassis isn't grounded then it floats at 60VAC.
[1] For transformers with more isolation they wrap the primary and secondary on top of each other. Less capacitance that way. Medical grade transformers have physically separate windings.