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11th Dec 2018, 9:46 pm | #1 |
Pentode
Join Date: Dec 2018
Location: County Meath, Ireland
Posts: 242
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UPS as Isolation transformer?
Folks,
Would a computer UPS act as an Isolation transformer? Ray |
11th Dec 2018, 10:02 pm | #2 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
Posts: 2,476
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Re: UPS as Isolation transformer?
I suspect not.
It depends on entirely on the UPS in question, some might be fully floating when used in battery backup mode, some will probably tie the N-E together throughout, besides when running normal bypass mode (mains healthy) they will in effect be direct online. Also the cheaper end ones run with a pseudo sine wave or more likely a rough approximation of something resembling a stepped square wave even in battery backup mode.
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I don't suffer from Insanity. I enjoy every minute of it. |
11th Dec 2018, 10:27 pm | #3 |
Pentode
Join Date: Dec 2018
Location: County Meath, Ireland
Posts: 242
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Re: UPS as Isolation transformer?
Thanks, I suspected as much regards to the N and E.
But just wanted to check. If I ran it in battery mode ( unplugged from mains) I guess it would by default be isolated. Cheers Ray |
11th Dec 2018, 10:56 pm | #4 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
Posts: 2,476
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Re: UPS as Isolation transformer?
Yes true, but the N-E could sill be connected together at the output side of the UPS internally even in battery backup mode so do check.
Edit: the N-E won't be connected together on the mains/primary side or else it would trip any RCD connected at source, however the battery backup side might.
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I don't suffer from Insanity. I enjoy every minute of it. Last edited by Red to black; 11th Dec 2018 at 11:03 pm. |
12th Dec 2018, 12:00 am | #5 |
Pentode
Join Date: Dec 2018
Location: County Meath, Ireland
Posts: 242
|
Re: UPS as Isolation transformer?
Nice one, I'll check it
Thanks Ray |
12th Dec 2018, 9:25 pm | #6 |
Pentode
Join Date: Dec 2018
Location: County Meath, Ireland
Posts: 242
|
Re: UPS as Isolation transformer?
Just another thought....
Wouldn't two of those building site 110v isolation transformers placed back to back do the job ? |
12th Dec 2018, 9:34 pm | #7 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
Posts: 2,476
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Re: UPS as Isolation transformer?
You could do, however don't connect the two 110V earths together (safely isolate these) as this is a centre tap as well on these transformers it could cause phasing/shorting problems and it also carries the Earth connection across from the primary side, which you don't want on a fully floating supply.
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I don't suffer from Insanity. I enjoy every minute of it. |
12th Dec 2018, 10:09 pm | #8 |
Pentode
Join Date: Dec 2018
Location: County Meath, Ireland
Posts: 242
|
Re: UPS as Isolation transformer?
Excellent, I just happened to have on of these in the work shed.
Now I also happen to have a 220/110v auto transformer which is not an isolation transformer. But it stands to reason I could use that combined with the above isolation trafo to create a 220v to 220v isolation system Your point on the earth's is well made , I should just safely ignore these and leave unconnected. |