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Thread: 1ph to 3ph Transformer Info Needed

  1. #31
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    True 2-phase actually has 90 degrees between phases, but it is quite rare. The usual 120/240 VAC power for US homes is actually single phase, or sometimes called "split phase", but there is no way to connect it to get 3 phase.




  2. #32

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    that makes a lot more sense. is there any useful application for this transformer in a residential area using the US single phase?

    thank you

  3. #33
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    Um, no?

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  4. #34
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    Quote Originally Posted by gravityworks View Post
    that makes a lot more sense. is there any useful application for this transformer in a residential area using the US single phase?

    thank you
    probably not. what you have is not a true 75kva transformer but a 37.5kva transformer with only a single coil, tapped in the middle. all it does is provide a midpoint to get 120/240v from a 240v input. probably intended to get 120/240 from a 240v delta supply.

    if you want you could rewire it as a 37kva 120v isolation transformer.

  5. #35
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    Quote Originally Posted by JRouche View Post
    I knew it!! Some one else has to have one of these massive 1ph-10hp GE motors.

    It really is a giant motor that I never understood why it was made. It is pretty comical how large this thing is. 168lbs in weight. I should compare it to my 7.5hp HF air pump motor. It prolly weighs 25-30lbs.

    I want to open the box and see whats inside. Prolly a gang of caps huh?

    GE made it so there are many of them out there. JR

    Crap Photo again

    JR there are thousands of those 10hp 1ph motors in service in the Agricultural Sector.In the pic is one I replaced last Oct from Grain Dryer,it only made 32 years being 25 ft on top of dryer in lots of dust with no cover,positioned Vertical PTO end up.It a dual fan Baldor with 40amp draw,PTO Bearing Failed it had moved Millions of Bushels of grain.
    There are quite a few 15hp 1ph motors in service running grain dryers that are nearly double the size of the 10hp,I beleive they are special purpose motors and not as common as 10hp.

  6. #36

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    Quote Originally Posted by johansen View Post
    probably not. what you have is not a true 75kva transformer but a 37.5kva transformer with only a single coil, tapped in the middle. all it does is provide a midpoint to get 120/240v from a 240v input. probably intended to get 120/240 from a 240v delta supply.

    if you want you could rewire it as a 37kva 120v isolation transformer.
    Probably too much to ask but can you show me how the wiring would look like if i wanted to use it as an isolation transformer for 120v/240v?

    Below is the picture of my current testing on the transformer with regular 240v Black and White wires going into tap 1 and 2 and the green Neutral wire is jumped between taps 3 and 4. i also have the measured voltages written down on a card on top of the transformer. Picture taken after Everything is disconnected by the way

    4 1 2 3

    5 7 6

    https://drive.google.com/open?id=1I9...g1bvHyaDgcEypY

    Info on tag outside the Enclosure:

    https://drive.google.com/open?id=1oH...z5Hy7jZLidXoWP

  7. #37
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    Bumping this back to the top. The last post got stuck overnight in the moderation filter.
    George

  8. #38
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    I found some info on 2 phase to 3 phase connections:

    http://machineryequipmentonline.com/...nd-vice-versa/


    However, that shows two magnetically isolated transformer cores, which I think is necessary for this to work. It seems like your transformer may have internal connections to windings on two cores. There is one winding 5-6 with center tap on 7, and one phase (B and C) of the two phase power connects to this winding to become phases B and C of the 3-phase output. The other phase of the two phase power (call it A and D) connects to 1 and 7, and the 86% tap 2 becomes three phase "A", which is 90 degrees to the B-C vector (phasor?). The 86.6% is the cosine of 30 degrees. There may be an isolated 240V winding on 3 and 4.

    You may need to see if any windings are electrically isolated, and if not, there is no way to use this as a single phase isolation transformer. But I think there must be isolation between the two 90 degree power pairs (A-D and B-C). You might then connect 240 VAC to, say, 3-4, and you might get isolated 240 VAC on 5-6 or 1-7, with perhaps 208 VAC on 2-7.

  9. #39
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    agree with Doozer, better to leave it three phase. RPC then to a 3P transformer to boost it up. Half my machines are 600V and this works perfectly. May even be cheaper than a new large hp single phase motor....."and then you have it"
    .

  10. #40
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    Mar 2015
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    Now that I have three phase power with an RPC, I am a tad partial to it. My RPC is quiet.

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