Quick question about transformer

Discussion in 'The Projects Forum' started by biscuitownz, Feb 20, 2014.

  1. biscuitownz

    Thread Starter New Member

    Aug 9, 2013
    25
    0
    So I have a toroidal transformer that has 2 120v primary and 1 120v secondary.

    I was wondering if I put the primary coils in series with 120vac as the source so each primary coil will technically see 60vac, if I do this will the secondary voltage output be lowered?
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,502
    380
    hi,
    Ensure that the End of one of the 120Vac primary windings is connected to the Start of the other 120Vac primary winding.
    With 120Vac applied to the free ends of these two series windings there should be 60Vac across the secondary.
    E
     
  3. biscuitownz

    Thread Starter New Member

    Aug 9, 2013
    25
    0
    Yes, thank you! I was aware that if it wasn't connected from one end to the start of the other it would essentially be in parallel. :D
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
  5. MrChips

    Moderator

    Oct 2, 2009
    12,432
    3,360
    No. That is not how to make a parallel connection.
    With two primary windings there are four ways you can connect them:

    1) series connection in phase
    2) series connection out of phase
    3) parallel connection in phase
    4) parallel connection out of phase

    What the previous posts are saying is make sure your connections are in phase.
     
    shortbus likes this.
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    (4) Parallel connection out of phase will be accompanied by a bang and having to replace the input fuse.
    Your VA rating will be reduced slightly by series 120v windings on 120v supply.
    The other more efficient way is to parallel the windings on 120v and remove secondary winding until voltage is desired level, approx 2turns/volt.
    Max.
     
  7. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    To perform the test safely, if you not sure about the phasing, put a 110V incandescent bulb in series with the primary winding. If the connection is correct, the lamp will glow weakly or not at all and you will measure 60Vac at the secondary. If the connection is incorrect the lamp will light brightly.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    Another simple test is to connect an end of each windings, power the other end of One winding, measure from unconnected end to the powered end of the first winding, the result should be near zero, if 120v then swap either pair.
    Max.
     
  9. biscuitownz

    Thread Starter New Member

    Aug 9, 2013
    25
    0
    Well I tried connecting it today but the secondary coil isn't giving me any power for some reason. I've tried one primary then the other, and also parallel/series. All of those combos don't give me any output from the sec coil.

    Here are some pics of it:

    http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/ieEAAMXQlgtSxBzQ/$_57.JPG
    http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/mJAAAOxycmBSxBzY/$_57.JPG
    http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/c4QAAOxy4dNSxBzI/$_57.JPG

    This is the same toroidal that I have: http://www.fvstore.com/Powertronix-...al-Isolation-Transformer-MIU-500/p733295.html

    This is the manufacture's website http://www.powertronix.com/medical_isolation.php### I can't seem to find a PDF or anything of that kind to get more information on it.
     
    Last edited: Feb 20, 2014
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    Seems expensive? One of the cheapest is Antek also on ebay as jonango
    http://www.antekinc.com/500va/
    Have you checked the resistance of each winding to confirm the three separate windings?
    Max.
     
  11. biscuitownz

    Thread Starter New Member

    Aug 9, 2013
    25
    0
    Yes, the two primary windings are 1~2.5ohms but the secondary leads are not reading anything on the meter. Which seems really strange...
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    That is your problem!
    Is there continuity to any other winding from the secondary leads.
    Max.
     
  13. biscuitownz

    Thread Starter New Member

    Aug 9, 2013
    25
    0
    Well, turns out the wire had some type of coating on it that was causing it. I scraped it off and it works great now!

    Thanks
     
  14. MrChips

    Moderator

    Oct 2, 2009
    12,432
    3,360
    No offence intended but it would appear that you lack the necessary knowledge and experience to be able to work safely with AC mains transformers. Get someone with the proper credentials to help you or post your questions and circuit diagrams here before turning on the power switch.
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    Yeah.. Enamel is not a good conductor.;)
    Max.
     
  16. biscuitownz

    Thread Starter New Member

    Aug 9, 2013
    25
    0
    I was building this.. :(

    [​IMG]
     
Loading...