Transformer wiring - Primary has 4 wire ends, secondary 2 ends

Discussion in 'General Electronics Chat' started by RogueRose, Oct 5, 2016.

  1. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4
    The model is 430-7101(3) and is from an APC UPS and there are 2 of these that run in series - Each has a 4 wire connection on the main board and the terminals on the mainboard look to be in parallel.

    I did a continuity test on the 4 wires and wire 1 & 3 and 2 & 4 signal as a single wire. Wire 2 (black) has a 15A 125v inline fuse and all wires are 16awg.

    Since this is a UPS, IDK which is considered primary as if it is being battery fed, then the larger gauge would be primary and step up the voltage.? But I didn't think DC could be stepped up like this, Could that be why there are 2 sets of wires on the high voltage side?

    I'm trying to find out what the output voltage is of the transformer and wanted to know what wires to use to test 120 AC. I was thinking that using 1 & 2 as + and 3 & 4 as - , but wanted t check if that would be correct (fusing concerned me)

    Actually after thinking about it, I think the 2 sets are for 120 and 240. When 120 is detected connector 2 and 3 are "shorted" to make a longer wire. Does that seem possible?

    transformer.jpg

    transformer2.jpg
     
    Last edited: Oct 5, 2016
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
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    If it is a transformer there would be different gauge windings.
    Can you see the windings ?
    Can you meashre the resistance of the windings ?

    I once got few of those from a 1.5KVA APC slim type UPS and they turned out to be just inductors....o_O
     
  3. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4

    The other side has 10awg windings

    I found this video which uses a similar transformer and it was from a similar UPS as this one. He has the 4 connector jumped in some way or it is the live wires connected to the outlet. It looks like he has connected 1 and 4. His transformer is larger than mine it seems.

    I tried hooking up 120 to connector 1 and 3 and it tripped a 15A Breaker immediately. 1 and 3 have continuity and 2 and 4 have continuity. So I thought running power through 1&3 or 2&4 would be the right thing. I'm looking for some other vids or posts of people testing units from these UPS's.

     
  4. tranzz4md

    Member

    Apr 10, 2015
    139
    28
    Yes the two windings are primary and would be connected either in parallel or series depending upon the input voltage. (parallel for 120v, series for 240, for example).

    I doubt that those two Transformers are connected in series but it is possible. Typically they be connected parallel to each other each performing a different function in the unit. They are connected to the AC input line ahead of any rectifiers.

    If these are older and smaller units one Transformer could be for the input line ahead of the rectifier and the other could be for the output line after the inverter.
     
    RogueRose likes this.
  5. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4
    Thanks for the reply. It is a 2200VA unit and both transformers are identical if that matters.

    I found a schematic for this unit but the board is a 0735 and mine is a 0734 rev 5. They seemed to make many revisions a year...
     
  6. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4
    I took pics of the board (better pics) and it shows the 2 transformer connectors clearly. They seem to be in parallel and I'm trying to confirm the primary winding's APC_Trans_1.jpg APC_Board_Front.jpg APC_Board_Back.jpg .
     
  7. tranzz4md

    Member

    Apr 10, 2015
    139
    28
    Well, I can't answer that without an understanding of what you mean by "primary", because the use of that term is pretty relative! Most people mean the higher voltage windings by primary, but some mean the windings connected to the feed side of the circuit-as opposed to the load side.

    Additionally, UPS designs do things with transformers that are very unusual, and I haven't really ever spent the time to work through their schematics to get a clear understanding of some of their games. They'd get rid of transformers if they could beat their inductive characteristics, and as R!F@@ implied, they sometimes use large, wound inductors.

    I thought I might give you some quick help, but let's see what some others have to say.
     
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I have used 650Va APC UPS transformers for countless projects.
    One project was use 4 them for a power amp project. It works to this day but I say the darn thing is heavy. But it does provide plenty of power.

    I cannot help OP.
    He did not provide the resistance measurements I asked for.
    He did not provide a complete transformer picture. I need to see the whole unit.
    Plus it would be easier if OP has a auto transformer to do some tests.
     
  9. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4

    I waited on the resistance measurements because I thought there was something wrong with my meter. I tested on an identical other transformer and the measurements were the same so it seems the meter is correct.

    16awg side:
    White/Black .6 - .7 ohm (initially read 1.3 for a second then would jump between .5 and .8 then settled at .6 - .7 ohm)
    Blue/yellow ~.1 ohm - would bounce between 0 and .1 but reached .2 on initial connection

    10awg side
    White/Black - .1 ohm - stable


    Trans_top.jpg Trans_top2.jpg
     
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