Isolation Transformers

It was apparently used in a hospital.

What is the Kva rating? It will say on the data plate.

Does it say ’Medical Grade’ anywhere on it?

If yes:
Most medical grade isolation transformer I have ran across float the secondary winding above ground. That means both AC Line contacts on the receptacle outlets are fed from Hot ungrounded legs, conductors. Neither of the two hot conductors have a reference to ground. Therein, not to the metal case/enclosure of the transformer or to the ground contact of the receptacle outlets.

I would suggest you use a volt meter and measure for voltage from both contacts to the equipment ground contact on the outlets.


If the isolation transformer is wired as a Grounded Power System:
Short slot of the outlet to equipment ground should measure 120VAC nominal. (You said it runs 124Vac.)Longer slot of the two, or ’T’ slot, the neutral contact should measure a solid zero volts to ground.

If the isolation transformer was left ungrounded then you have an Isolated Power System. Any voltage readings from either contact to ground will be phantom voltage. Usually a digital meter reading will be all over the place and will not hold steady.

Medical grade transformers are meant to be used by qualified personnel only.
If your transformer floats the secondary above ground you should have an electrician wire it as a grounded power system. It’s simple do.

.

When did they start printing ’hospital grade’ on anything that was? dang, has it really changed that much since I was in the field? OP did say older isolation transformer?

I guess things have: Hospital grade receptacles include the same markings that appear on general use receptacles, and also include “Hospital Grade” or “Hosp. Grade”, typically on the back of the receptacle where visible during installation

Wasn’t always so. I guess code revisions took a big friggin change to assure no mistake. Guess they factored in no one pays attention to the spec sheets any longer. ..hmph
Reminds me of those on the job concentrating solely on their electrical prints and were clueless to look at the architectural and others...*laffs

In Australia 230v to 230v isolation transformers I have use them on my source gear since the 80’s. they provide "Galvanic Isolation" from the mains and block/filter any dc on the mains.

For the US
http://www.surplussales.com/item/_tp/91092-12.html
https://www.bkprecision.com/products/power-supplies/1604A-single-output-isolation-transformer.html

Cheers George

oicu812

41 posts
04-10-2019 6:34pm

When did they start printing ’hospital grade’ on anything that was? dang, has it really changed that much since I was in the field? OP did say older isolation transformer?

@ oicu812

Medical grade.
Example of:   
https://www.tripplite.com/isolator-series-120v-1000w-ul60601-1-medical-grade-isolation-transformer-4....

As others have said, isolation transformers don't regulate, and they don't even really isolate, except in the sense of from DC. It helps to understand how they work in the first place. That alone will answer a lot of questions. Do a search.

Sounds like the one you're using is pretty close to 1:1. Getting a few volts more out than in tells you the windings aren't equal, its not a perfect 1:1 but again, read up and learn how they work.

The one I use is audiophile grade 2:1 step down, the supposed advantage being you can run 240v to the transformer and get 120v out the other end. Which is what I do, and it is better than the exact same wire and connections that were running 120v before.

Of course if you listen to half the guys around here I am long since dead and buried, along with the half the neighborhood I burned down, voiding warranties, experimenting with lethal blah blah blah yada yada.

As if any of this matters. Because it don't. What matters, the only pro's and con's as you put it, is what you heard. If you didn't hear any improvement then sorry, waste of money. If you did, well then you can tell by how much it was worth it. Them's the pro's. All the rest is a con.