Hello,
I found an old Siemens transformer that I wanted to reuse as an isolation transformer, but I'm not sure how to interpret it, firstly because I'm very familiar with industrial-like transformers, and it's written in German.
From some images I read, the diagram defines where we should apply a "jumper" (again it's in German, so not able to interpret). i.e., shall I connect 37 and 38 to supply 220V our of the secondary ? I saw some images in the internet where I see a jumperwire between 37 and 38, but I not 100% sure. But more important, how should interpret the primary to have a 220 input. link 23 and 26?
I'd rather ask for help than do something stupid. Thank you in advance for your support.
Thanks
Hi,
This is a fairly complicated transformer and may possibly be made for a special purpose. That makes it very unknown more so than most other transformers. That means you have to test it, there's no other way. Before you can parallel any windings you have to test for voltage AND phase. If the phase of one winding is opposite to what you think it is, the transformer windings can blow or you blow the fuse or circuit breaker.
The idea would be to discover the voltage and the phase of each winding so you can create the schematic with all voltages shown clearly. That would mean you can get a lot of different output voltages, and easily figure out what goes where.
It does look like the top two windings are 110vac each. If you connect the two centermost terminals of those, you get 220vac on the two outermost terminals, with the right windings on the lower set connected correctly. That gives us a convenient place to start.
By applying 110v to one of those windings or 220vac across the outer two, you can easily measure the voltage of the lower windings, every single one. You can then label each winding with the voltage you measure. If you use a light bulb in series, then you have to measure the actual voltage across the 110vac winding also and do the math to get the actual winding voltage on the lower windings (as if 110vac was really applied without the light bulb). This would quickly wrap this up, but you do have to measure the phase too.
To measure the phases, you connect the center most two terminals of the lower windings together and then check the voltage across those windings like you did before, except now you look for either a voltage increase or a voltage decrease. If the voltage increases, then the windings are of the same phase (left most terminal on one winding is the same phase as the left most terminal on the second winding).
Once you get all this information it should be easy to figure out what windings you have to connect and any jumpers, and also figure out ANY combination of winding connections that are possible and the output voltages from that.
The remaining possibility is that there are actually two transformers in one case. The leftmost transformer and the rightmost transformer. This would mean other connections might be possible. If you take more pictures especially of the sides of the transformer, this might help figure this question out.
To parallel two windings you have to first find the phase of each winding, and assuming that the leftmost terminal of each winding is the same phase, you connect the two leftmost terminals together and the two rightmost terminals together. You only have to do that though if you need the full power output.
The power outputs bring up another question. How much power can you draw from each winding.
To find that out the best way is to look at the diameter of each wire lead where it connects to the respective screw. You can infer the current rating from that and with the measured voltages you can calculate the power ratings.
If you need a diagram I can draw one up for you. Wordy descriptions in electrical work do not always come out clear enough that's why we draw schematics