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3 phase electricity Q's

Discussion in 'The Lounge' started by ryan22re, Mar 27, 2007.

  1. ryan22re

    ryan22re 1/2 ton status

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    Anybody have any three phase equipment in their garage running off of single phase?

    The big hold up -until now- for my power steering pump dyno was the ability to run a three pahse motor off of single phase electricity.

    I found static transformers/converters, but they don't let the electric motor run to it's rated HP. Usually 75-80% of rated. Plus they are over 100 bucks when you need to run a 5 hp motor.

    But a rotary phase converter seems to be the real deal. Problem is that they are expensive to buy new. You get the full rated HP of your motor too. But the $$$ is the hold up. Usually over $500 for a 5 hp or more converter.

    It seems that you can turn a three phase motor into a three phase converter to drive the real motor. So you'd need two 5 hp motors. One to convert single to three phase and one that does the work. Getting the motors shoudn't be a problem.

    I found some guides/plans online, and have talked to both an industrial electrician and an electrical engineer and they say that it is very possible. But, does anybody have any firsthand experience with these?
     
  2. Jagged

    Jagged 1 ton status

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    Remember you will lose some energy between the two motors. No motor is 100% effecient.
     
  3. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    Rotary phase converters are a step up from a static phase converter. They are basically a static phase converter running a three phase motor (called the idler, no load on this motor). Then you get your three phases off the terminals of the idler motor. It's important to use the right capacitors between phases to get a balanced output on the idler motor. How many horses on the motor you are trying to run? A VFD might suit you better, the ones that turn single into three phase only go up to three Hp. I assume the online plans you found are these:

    http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

    I run a 2Hp motor on my lathe with a static phase converter, but it is easy to overload it. I was going to try to build a rotary phase convertor, but have yet to find a 3-5Hp motor to use as an idler. So, I'm going to see if my shop will buy me a VFD at wholesale. Not only do these have the phase conversion feature, but they are good for speed control and dynamic braking. The Hitachi L100 and L200 are known to be good units. These can be found on the bay from time to time in the $100-200 range. I do believe BadDog made his own rotary phase converter, might wanna pick his brain.
     
  4. Leper

    Leper 1/2 ton status

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    A buddy of mine wanted to do that, so I found him some plans and he made one. He already had a 3 or 5 HP electric motor. Would you like a copy of the plans if I can find em?
     
  5. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    I have the plans, see above link.:wink1:
     
  6. Leper

    Leper 1/2 ton status

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    oops
     
  7. darkshadow

    darkshadow 1 ton status

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    that is where it is at, my brother (electriction) has one set up at home, for dicking a round, with a digital hertz controler on it and every thing, runs the 3 phase moter, at any exact rpm, no problem, but the expence is the tough thing, I am pretty sure he scored his free, could ask him when he gets back from cuba. (jerk ;))
     
  8. ryan22re

    ryan22re 1/2 ton status

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    Initially, I'm going to try to set it up with 5 hp motor. I had one of the hydraulic engineers calculate what kind of HP I would need to run a PS pump the way that I want too. We came up with an estimate of 3.4-4.0 HP, depending on temp of fluid. I'll really have to try it and see.

    Yes, that is the guide/instructions I found. I realize that it won't be 100% efficient. I would really like to overkill the thing and find some 7.5-10 hp motors. A frequency controller would be key, but to get the pump down to idle speed, I'm gonna try and mess around with pulley sizes.

    Thanks for the replies.
     
  9. darkshadow

    darkshadow 1 ton status

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    that much to run a PS pump huh?

    pully idea is good, should be a little cheaper too.
     
  10. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    Does electrical horsepower equal internal combustion engine horsepower? I would guess it does, but I have some doubts. FWIW 1 Hp=746 Watts.
     
  11. ryan22re

    ryan22re 1/2 ton status

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    The calculation was for an electric drive motor, so I think it is close enough.

    Looks like I found a guy on ebay selling the right kind of capacitors for cheap and my electrical guy at work is willing to give it a shot.
     

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