Isolation transformer source

I'm in the UK so it's 240 volts, but found it a lot cheaper to buy the transformer bare and box it up myself. They're not a mass produced device like say a 240 - 110 type so that may be the reason.

They used to be common for stage etc use, but RCDs etc seem to have replaced them. As well as safer electronic instrument design.

They might well come up on Ebay secondhand, though.

I think the $100 and "good quality" exclude each other for a transformer that size.

the smaller units as used with cash registers and POS systems tend to max out at 4 amps.

is used is ok, look for stuff from acme, topaz, oneac, shape, powervar. powervar even had some interesting ones based off toroidal tranformers if you want the ooh and aah factor.

A 625VA toroidal in the UK would cost about 50 gbp as a bare unit. Slightly more for a one off.

Not cheap. Surplus Sales of Nebraska has some.

Depending on what your going to do, check if it has the secondary to ground bonding which you should remove if you are seaking ground isolation.

greg

Here's one on eBay. 4.35A for about $75 delivered.

PlainBill

I'd avoid surplus sales. Why pay twice new prices for old stuff when you don't have to?

It's an interesting place browse, and I've been there in person, but the ripoff factor is pretty incredible.

"JW"

There are two:

1. Galvanic isolation - for use on a service bench.
2. Neutral conductor isolation.

Most you see offered for sale in the USA are of the *second* kind.

.... Phil

Surplus sales has its place in the food chain. Its NOT a salvage place that just haphazardly throws stuff in piles, its all gone through sorted,labeled and cataloged. Lots of nice old ham gear stuff if you into it. Yea, most of it is not cheap. but try to find some of it from other sources. Some of the stuff they have will NEVER sell at the prices they have it at. Everyone knows how hot tube oscilloscopes are.....

With the number of shops closing, i would wait for a going out of business sale or Ebay.

bob

You could always salvage a couple of microwave oven transformers and connect them back to back. Make sure and disconnect the secondaries from the cores though, of course.

Jon

"Jon Danniken"

Absolutely WILL NOT WORK.

..... Phil

MCM Electronics has one. Chuck

Surely an isolation transformer is just that - a one to one device with DC isolation between windings. How it is subsequently configured is a different matter. One use is where you can't be sure the line and neutral of the supply are connected correctly - if they have a ground reference.

"Chuck"

.... Phil

Referring to one (1) of 'em

I think

Yep, they have 'em.

-- Cheers, WB .............

I think the whole basis for surplus sales is the guy has a really large building, and can store infinite amounts of crap inside it forever. Storing something there for decades doesn't seem to waste any space or compete with shelf space for stuff that does sell.

It's a fun place to checkout if you're ever in Omaha. Lots of stuff on the floor you can walk around isn't on the website.

Unfortunately the next best place like that that was in chicago called the Radio TV Lab closed years ago. It was a serious time machine in there. The guy had NIB replacement parts for wire recorders- and not ones from planes, but from before magnetic tape worked at all, plus service guides for pretty much anything with tubes in it. Getting in and out of the shop was a single file line type operation and people having to all leave to let customers out wasn't uncommon. Stuff was stacked to the ceilings in every direction. If you needed a part that wasn't current it was there.

Maybe somebody here knows what this-

He had some sort of capacitor that looked like a large can electrolytic but it was filled with liquid that sloshed around. I don't recall the ratings at all.

It was explained that if shaken, and if the case started to feel colder the cap was still good, sort of like an chemical ice pack.

Does anybody have any idea what sort of capacitor this was?

I've been tempted to try that just to see how awful the regulation is and what sort of waveform would even come out before the things burned up.

An isolation transfor is typically 1:1.1 in real life. Its acts as 1:1 with FULL load. Well all transformers are rated FULL LOAD.

They really need to start calling these things different names. A regular "isolation transformer", and they should not be calling it that, is NOT ground isolated since the secondary is tied to ground. The purpose of this transformer is noise reduction, period, using an isolation transformer.

Find another name.

greg

In the UK the secondary of a (safety) isolating transformer is *not* tied to ground - that would entirely defeat the purpose.

So someone needs to invent a new name for your type. ;-)

"Dave Plowman "Pommy Nutcase"

... Phil