Is a 115v/6v transformer basically the same as a 230v/12v? Assuming same power rating.

Discussion in 'General Electronics Chat' started by Smiley, Dec 29, 2014.

  1. Smiley

    Thread Starter New Member

    Dec 29, 2014
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    I’m kind of an electronics newbie and apologize beforehand if this is a stupid question and I’m pretty sure the answer is basically yes, but I thought I would post to be sure. I’m repairing a speed circuit board on a power tool and need to replace a small AC transformer but am having trouble locating a similar device. I found the following part on digikey that appears to be an exact replacement, but have contacted them and they’ve indicated that it is an obsolete part and they can no longer get it.

    Attached is the datasheet for the transformer, part number BV020-5411.0 This is a small 115v primary/6v secondary, 58mA (0.35VA), epoxy encapsulated transformer, PCB mount with 15mm spacing on primary pins and 5mm on secondary pins (15mm between primary and secondary). I’ve done some exhaustive online searching and haven’t been able to come up with another direct equivalent. But it appears that I might have better luck finding a 230v/12v version with a similar pinout. If I can use the 230v/12v one instead, do I need to find one capable of 0.35VA, or do I actually need double that (0.70VA) since I will be using it in a 115v application?

    Furthermore, I’ve found several transformers with dual primary/dual secondary windings that may also work. Could I use a transformer with two 115v inputs, and two 6v outputs and wire the primaries in parallel and the secondaries in parallel? I would need to slightly modify the pins and add a couple jumper wires under the transformer to make it fit, but I suppose that could be an alternative.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes that OK as long as you connect the parallel windings in phase, IOW the black dot mark indicates identical or parallel connections.
    The secondary current or va will be the same for 120/240.
    BTW, did you check the Hammond transformer site?
    Max.
     
  3. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    From 6 volts, 58 ma, the 12 volt version must also be rated for 58 ma so the secondary wire will be large enough, and that's .7VA
     
  4. Smiley

    Thread Starter New Member

    Dec 29, 2014
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    Tanks for the replies. Yes, I did check the Hammond site and wasn't able to find anything close. MaxHeadRoom, I'm not sure I completely follow your comment on connecting them in phase. If I do use a transformer with dual primary and dual secondary, I was planning on connecting pins 1 to 3, 2 to 4, 5 to 7 and 6 to 8. Basically so that the primary matches the secondary.

    Thanks for your help. This opens up my options a bit.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you look at some of the diagrams on the hammond site for Txr's with dual pri/sec you will notice a black dot at one end of the winding, when paralleling each set of windings, the ends with the black dot have to be connected together, the other pair are then connected.
    When paralleling it is important to get the phase right, otherwise you short the winding, if you have a Txr that is not marked, you can find out the correct way by connecting one end of each winding together and measuring the open ends, the correct way will show close to zero voltage, if it is wrong you will see double the sec voltage across the open ends.
    Max.
     
  6. Smiley

    Thread Starter New Member

    Dec 29, 2014
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    Thanks again:
    As you were responding, I just happened to be on Hammond site and found this http://www.hammondmfg.com/5CHook.htm just as you described thanks again, and I'll keep your advice about unmarked windings.
     
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