Help with transformer 220V - something

[Bassalisk]

I sort of understood that. I find it hard to understand just why they did it that way, though. Perhaps they got a job lot of 110V transformers from the states and were determined to use them one way or another. It clearly worked ok that way.
I should still be interested in the actual circuit they have used. The photos don't really have enough info in them to be sure of how things are connected in the original layout.

@Jim - Have you any ideas?

I have variable AC source at my faculty. I will take it tomorrow or today, and test it.

 

[sophiecentaur]

Well i tested it with my multimeter. And the 110V ports on both sides are short circuited.
...

Now I am really confused

How can it be that there absolutely no info on this on the internet, schematics at least.

A multimeter will not distinguish between the different ends of a reasonable quality transformer winding - they are ideally, zero resistance. Your low voltage AC supply should sort a lot of this out for you.

Hah! there is lots of stuff that's not on the internet - or, at least, not easy to search for. But why would you expect anyone to e-publish the design / user / maintenance manual of a bit of specialist kit? What you need is a big fat technical book about the general use of transformers.

I would warn you against assuming that those transformers are 220V each. It's more likely, imo, that the "220" refers to the optional way they have been connected together (primaries in series) . I would expect to see a similar bit of kit in the US with "110" and which is wired differently (primaries in parallel).

I have thought some more about this and I am getting there.
If the transformers were made to be well matched (and that's the crux) then there's no basic reason why the secondaries shouldn't be connected directly in parallel. All that's necessary is for the primaries to be connected so that the polarities of the secondaries is the same. Otherwise you have a serious smoke making machine with two voltage sources connected head to tail with no series resistance! When the primaries are connected to 220V in series, the secondaries need to have the same number of turns and to have the same load. Putting them in parallel will mean that they will have the same volts across them whatever load is there so the loads on both primaries will be equal. If there were a small difference in the number of turns on the secondary windings then this would not be too desperate; the two secondaries would just 'see' slightly different loads and so the centre point would not be exactly 110V. I don't think that would matter too much.

btw, I just found this link. Looks familiar??

 

[Bassalisk]

A multimeter will not distinguish between the different ends of a reasonable quality transformer winding - they are ideally, zero resistance. Your low voltage AC supply should sort a lot of this out for you.

Hah! there is lots of stuff that's not on the internet - or, at least, not easy to search for. But why would you expect anyone to e-publish the design / user / maintenance manual of a bit of specialist kit? What you need is a big fat technical book about the general use of transformers.

I would warn you against assuming that those transformers are 220V each. It's more likely, imo, that the "220" refers to the optional way they have been connected together (primaries in series) . I would expect to see a similar bit of kit in the US with "110" and which is wired differently (primaries in parallel).

I have thought some more about this and I am getting there.
If the transformers were made to be well matched (and that's the crux) then there's no basic reason why the secondaries shouldn't be connected directly in parallel. All that's necessary is for the primaries to be connected so that the polarities of the secondaries is the same. Otherwise you have a serious smoke making machine with two voltage sources connected head to tail with no series resistance! When the primaries are connected to 220V in series, the secondaries need to have the same number of turns and to have the same load. Putting them in parallel will mean that they will have the same volts across them whatever load is there so the loads on both primaries will be equal. If there were a small difference in the number of turns on the secondary windings then this would not be too desperate; the two secondaries would just 'see' slightly different loads and so the centre point would not be exactly 110V. I don't think that would matter too much.

btw, I just found this link. Looks familiar??

But still it was used in printing, here in Europe, it should be 220V.

We will know for sure tomorrow or after tomorrow, I have some good folks at my university that have access to instruments and they will be willing to give me the privilege to use those instruments to test this transformer.

This has became more of a riddle than actually using it for a project :D

I will check that link out.

 

[sophiecentaur]

Yes - the two TOGETHER work at 220V. They are in series and they have equal secondary loads so the primaries simply share the 220V, getting 110V each. That "220" sign you have refers to the whole setup and the 0,100,110,120 marked on each transformer are the volts appropriate for each transformer on its own. (Let's face it, what's marked on the windings is pretty unequivocal).
Your original equipment was used in Europe but that doesn't mean that a version (or a planned version) of it -or even just the power supply - wasn't used (or planned to be used) in the US.
The bottom line is that it's a funny setup (though not as unusual as I thought, possibly) and could have been done with a single 'regular' 220V transformer. At least it's given some entertainment - and a bit of frustration. But there's no such thing as a free lunch.

 

[Bassalisk]

But there's no such thing as a free lunch.

In deed :D

 

[sophiecentaur]

So, as long as you connect all the relevant secondary windings in parallel and the two primaries in series, you should be OK, I think. Enjoy your lunch lol.

 

[Bassalisk]

Bad news.

I've took it to variac like suggested. And it turns out primaries are short circuited at one side, and open - ended between sides.

We blew the fuse in the process.

So this transformer is not of use.

Gonna go look for old amplifiers and take the transformer out of there.

Thank you all for your help!

 

[sophiecentaur]

But didn't we learn a lot?

 

[Bassalisk]

But didn't we learn a lot?

Nope, it just became more mysterious. Imagine what would I have done if I tested it at home at 220V.

We used 15-30V AC. Expected 5V at secondary.


Got a lot of sparks and a blown fuse. But luckily nobody got hurt.

 

[jim hardy]

Sorry guys, been away from 'net a couple days travelling..

Now trying to learn this darn laptop - old dog new tricks you know...

that's interesting - so the transformer has two sets of terminals labelled "0" "120, and they're not on two separate windings?
Zero ohms from "0" on one side to "0" on the other side?
Likewise 120?

Where did you connect your 15 VAC?

Curious indeed. I sure expected each to have two primaries wired in series, by a wire between 120 one side and zero other side..

So it goes, live & learn...

 

[Bassalisk]

Sorry guys, been away from 'net a couple days travelling..

Now trying to learn this darn laptop - old dog new tricks you know...

that's interesting - so the transformer has two sets of terminals labelled "0" "120, and they're not on two separate windings?
Zero ohms from "0" on one side to "0" on the other side?
Likewise 120?

Where did you connect your 15 VAC?

Curious indeed. I sure expected each to have two primaries wired in series, by a wire between 120 one side and zero other side..

So it goes, live & learn...

Its a very special transformer. Guess we will never know.


On one side(primary) they are short circuited(among themselves). Likewise on the other side.

But from one side to the other(primary) there is not galvanic connection(open ended).