Help with transformer 220V - something

[sophiecentaur]

Presumable this is a European built beast so it would be expected to take single phase 220V. The blue and brown leads sort of confirm this (along with the stripey European Earth wires).
But I am now totally confused because the earlier pictures are not the same as the later pictures. The earlier picture shows a blue lead going to both halves and to the 0V teminal but the later picture shows grey wires (the same one? joining the 0V on one half to the 110V on the other. Have you changed something?

Is this all to do with making the equipment re-configurable for use with 110V in the US, I wonder? I don't see any advantage in that system compared with having a double length (220V) primary winding on one core with a 110V tap half way up.

But I really have a problem in seeing exactly how the two halves, connected in series, can work 'properly' when fed with 220V because the share of the 220V that each half gets will depend upon the secondary load that each half is presented with. Weird. Looking at the secondary connections, it seems that they are connected in parallel and that would, presumably present equal loads to the two halves which, in turn, would tend to balance up and cause the mid point (grey) to float 'half way in between' the live and neutral connections. It should not, presumably, be connected to any ground but just be allowed to float.

@Bassalisk it could be a good idea to try and draw a circuit diagram of the system but I appreciate that it could cause some brain ache if you aren't familiar with that exercise. I can't see where those yellow wires are going and I'm also confused about what happens to the purple (9V) wires too. Are they just joining the secondaries in parallel?

 

[Bassalisk]

Presumable this is a European built beast so it would be expected to take single phase 220V. The blue and brown leads sort of confirm this (along with the stripey European Earth wires).

I disassembled them into separate transformers.

On the side of the transformer, there is a marking that says 220 (1 transformer) other one is not marked. Its more of a sticker than a mark.

 

[Bassalisk]

@Bassalisk it could be a good idea to try and draw a circuit diagram of the system but I appreciate that it could cause some brain ache if you aren't familiar with that exercise. I can't see where those yellow wires are going and I'm also confused about what happens to the purple (9V) wires too. Are they just joining the secondaries in parallel?

Those yellow and purple wires are in parallel with the other transformer.

I now realize that these 2 transformer where in parallel 100%.

That blue wire is connected to the 0 on the other transformer and brown is connected to the 110V.

So yes they were in parallel. Which means they are 220V transformers, now we have to figure out how are they working.

I am puzzled with primaries going to primaries on one transformer too.

 

[Bassalisk]

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.

 

[sophiecentaur]

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?

 

[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).