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Thread: 1ph to 3ph Transformer Info Needed

  1. #1
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    Default 1ph to 3ph Transformer Info Needed

    Was wondering if Transformer in pic would power a 575 volt Mill 7-1/2hp plus 1-1/2hp on Table Feeds.Can this be done by hooking Transformer to 240 1ph then pull 3ph 575 volts out? Thanks!

  2. #2
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    This is a step up transformer? Still need to generate the 3rd leg.

  3. #3
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    TTT, the nameplate shows it to be a single phase transformer that is designed to be hooked up to a 600V source on the primary side to give a 120V secondary output if the secondary windings are internally hooked up in parallel or a split phase 120V/240V output if the secondary windings are internally hooked up in series.

    This transformer would be used in an industrial setting (where the main three phase transformer's (Y) output is 347V to neutral and 600V phase to phase) to provide split phase 120/240V where needed.

    Backfeeding it from a 240V source will only result in a single phase 600V output.
    Last edited by Arcane; 08-04-2019 at 07:41 PM.

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    Looks too small for the load.
    My friend had a 7 HP Lathe which I considered to be about 7 KW (starting load is always greater)
    I took a 11 KVA (KW) 480 to 240 transformer and used it as a step up from 240 to 480.
    That fed a 10 KVA Hitachi VFD with single phase 480 and got 3 phase 480 output for the motor.
    So it can be done , but you need surplus and a 600 volt VFD
    You could do a static 600 convertor , but the caps would be extraordinary
    Rich

  5. #5
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    for milling machine duty, you can safely pull 5hp out of a 7.5hp 600v motor, by driving it from a 480v vfd.

    if you program the vfd for 480v 45hz, then you can get full torque from the milling machine at or below 75% of the nominal rpms. above that torque will drop and hp will be about constant.

    you may be able to rewire the motor for 347v delta quite easily, just program the vfd accordingly, you will need a 10hp 480v vfd to drive a 347v 7.5hp motor at full torque (but you need a 10hp vfd any ways to accept single phase input)
    Last edited by johansen; 08-04-2019 at 08:03 PM.

  6. #6
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    You cant get three phase out of a single phase transformer.

    Best case is rotary phase converter into a 3 phase 240 to 575/600v transformer.

  7. #7
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    assuming the goal is 600 3P, you could use it to step up to 600 1P then into a VFD....I've done that with 440V and it worked very well
    .

  8. #8
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    Most such transformers are designed for step-down application, and the output voltages are specified at full load. A typical transformer of this size has a regulation of about 5%, which means that the turns ratio is actually 600:126 or 600:252. Used as a step-up, 240 VAC will provide 571 VAC open circuit, and 544 VAC at full load. The nameplate also shows a set of taps on the primary that can adjust the voltage.

    The actual regulation of this transformer is stated on the nameplate as 4.7% impedance, which is essentially the same thing.

    You can't get three phase from a single phase transformer, but you can use two of them.

    And you might be able to use a 7.5 kVA transformer as an autotransformer (non-isolated) to get as much as 15 kVA. That is usually done with a transformer having equal primary and secondary windings, so a 240:240 7.5 kVA isolation transformer can be used as a step-up autotransformer to get 480 VAC at 15 kVA. This is because the windings are rated for 62.5 amps, so the output can be 62.5 amps at 480V. The primary current will be 125 amps at 240V, but current in the windings is 62.5A.

  9. #9
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    Thanks Guys for all the good info,I misunderstood the rating on transformer.I thought a step down transformer 600 volt 3ph to 240 volt 1ph could be fed backward with 1ph and 3 ph good be taken from that.

  10. #10
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    Quote Originally Posted by Tundra Twin Track View Post
    Thanks Guys for all the good info,I misunderstood the rating on transformer.I thought a step down transformer 600 volt 3ph to 240 volt 1ph could be fed backward with 1ph and 3 ph good be taken from that.
    Well, you need three sine waves 120 degrees apart. As far as I know, the 3rd leg has to be generated in phase, how a rotary phase converter works, or done digitally with a VFD. How is a transformer going to do that?

    Sent from my SM-G950U1 using Tapatalk

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