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3-phase ac motor

  1. Aug 16, 2015 #1
    Does anyone of a transformer that can step up 120vac to 460vac? Or do I need to use two transformers and step it up twice? It is powering a 10hp 460vac 3phase ac motor. Thanks.
  2. jcsd
  3. Aug 17, 2015 #2


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    Staff: Mentor

    First question, the 120V AC you plan to use....is that available in 3 phases?
  4. Aug 17, 2015 #3
    Normal ac outlet in office building
  5. Aug 17, 2015 #4


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    Staff: Mentor

    I think that's "No three phase available" answer? So that's a serious setback to your planning.

    Despite this, go ahead and work out how many watts equate to 10 hp, and compare this figure with the typical wattage rating in your country for ordinary office outlets.
  6. Aug 17, 2015 #5


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    Staff: Mentor

    ...er, you can't power a 10 hp motor (8kW) from a 120V office outlet (2 kW).
  7. Aug 17, 2015 #6


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    I am also trying to figure out how the OP figures a regular office building 120 volt outlet will provide 3 phase.
  8. Aug 17, 2015 #7
    True. I would need some big caps, it's about 10000 watts to power the motor how we want.
  9. Aug 17, 2015 #8
    Caps will not help - we are taking about power ( 10Kw ~ 460 x 12.6A x Sqrt(3) for the 3 Ph motor - at 120 Single phase 10Kw ~ 120V x 83Amps) . If you have access to the Circuit panel you could wire a Variable Frequency Drive set up for single phase input with 3 phase output, but that still will not "step up" the voltage you need.

    Preferably you can get 240VAC (most 120V systems in the USA are split phase 120/240) - so then use a 12+ KVA 240 to 460 single phase transformer. Then a Drive that can provide 10 HP with single phase input, I am sure it exists, but that it pretty large for the single phase and I have not found on in a quick search. Typically drive will have poor power factor and high harmonics ( THD) - requiring more hardware - filters etc....

    Try to find a 460V Source.
  10. Aug 17, 2015 #9
    Oh - also such a large single phase load may not be allowed by your utility and or local code.
  11. Aug 18, 2015 #10


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    Gold Member

    10 HP is a lot of power for a machine in an office - are you sure you actually need that much ??

    Is there a possibility of thinking afresh with a new lower assessment of power requirement ??

    Dropping power requirement and selecting a motor suitable for purpose and which will run on available electric supply will make life a lot easier for you .

    If using original 10HP motor is essential then only solution is to have a proper three phase supply with suitable power rating installed .
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