Phase converter

  1. Hopefuldave Intergalactic pot-mender

    Messages:
    1,705
    Location:
    The Shed of Danger, surrey, England
    A pony motor and belts/pulleys/ropes/whatever seems like more work to me!
    I'll have a look-see what cap starts my 7.5 HP motor and let you know what value - are you going for 240 or 415?

    Dave H. (the other one)
     
    maz0 likes this.
  2. Hopefuldave Intergalactic pot-mender

    Messages:
    1,705
    Location:
    The Shed of Danger, surrey, England
    Blimey, I've been Keeping Records...

    7.5 on 240 would want 400-600 uF start cap, live (well, one supply line) to generated phase, on 415 150-200 uF
    Balancing caps start about 125-150 uF live to generated, 70-85 uF neutral to generated on 240, 40-50 Live to generated, 25-30 neutral to generated on 415.
    These are starting guesses, you may need to add/remove a bit to get a) good voltage balance (with the load attached) and b)good power factor (find the value that gives lowest input current, then step back a bit)

    It's Very Sensible to put bleed resistors across the start capacitors, saves on unpleasant surprises - on 240 2w 39kOhm would work, on 415 2w 100K - on the start cap(s) only, the balancing caps will discharge through the motor windings

    Dave H. (the other one)
     
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  3. Retired Forum Supporter

    Messages:
    363
    Location:
    Huddersfield. UK.
    Hi,

    I ran my own 3 phase 415V installation for about ten years it costing under £120 to install; the transformer weighed around 75kg. I found the details on eBay and spent £17 for the three instructional DVD's from America. It's called "unique3phase" and I must have been the first here in the UK to install it successfully; I used to run my big extractor and ten speed industrial bandsaw from it; this gave full power just like having 3 phase from the electricity company installed.

    I dreamt up using a "shuttle" to add the coils and I'm credited by Doug the creator for this. This big transformer was so quiet I added a large lamp to indicate it was powered up; at idle it only pulled 0.8A. When I had installed mine Doug put a guy in Wales in touch with me; this guy wanted to run two big heat pumps into his farmhouses; I suggested using Doug's transformer method but he decided to go with a big rotary converter; after he had installed it he emailed once again for my advice; the converter was keeping his whole family awake at night due to noise.

    I sold my big machines a while ago and sold the transformer to a friend who is a sparky so I was happy I wouldn't be electrocuting anyone.

    For full details please contact Doug;

    http://unique3phase.com/

    Kind regards, Colin.

    3 phase_0001.JPG

    Adding coils using my shuttle idea.

    3 phase_0002.JPG

    Rock steady 415V.

    3 phase_0003.JPG

    75kg of beast.

    Under power on test..JPG

    I won't discuss how this is done because it's so highly dangerous and I don't want to electrocute anyone. Please contact Doug direct if interested I'm just adding this to let members know it's available. Here it's on test under power.
     
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  4. Hopefuldave Intergalactic pot-mender

    Messages:
    1,705
    Location:
    The Shed of Danger, surrey, England
    I read on another forum that everything on those DVDs can be found in an evening or two through google - how lazy are we, though?
    It's just a static convertor run from a step-up autotransformer, the "generated" leg is run at a higher voltage than the others to allow for the usual carppy static-convertor motor power loss by boosting the start and run capacitors' source voltages a bit. Nothing magical, not efficient.

    I put my RPC together mostly from what I found on Practical Machinist (they have a forum for them) for the "mains power" side, a bit of head-scratching for the control circuits, took longer to draw 'em up to jog my memory when needed than to work out how...

    Dave H. (the other one)

    P.S. - my converter would have come in well under £120 had I not wanted bells and whistles like volt and current meters on each phase, RCD on the output, relay logic and fault alerts etc... I haggle, and watch out for bargains :)
     
    maz0 likes this.
  5. Seadog

    Seadog Forum Supporter

    Messages:
    6,571
    Location:
    NE London - UK

    I've said words to this effect before. It is not true 3-phase despite protestations to the contrary.
     
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  6. Seadog

    Seadog Forum Supporter

    Messages:
    6,571
    Location:
    NE London - UK
    johnny max and Retired like this.
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