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Converting a 3phase 3hp motor to single phase

Discussion in 'Electrics UK' started by Robert Peel, 18 Sep 2021.

  1. Robert Peel

    Robert Peel

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    I was recently given a DeWalt radial saw from a factory I work in.
    The motor on the saw is 415V 2.2KW 3HP but on the junction box it says it could be wired in delta @ 240v, hence the reason why I took it home.
    When I opened it, there were only three wires, making it 415v only. I then spoke to someone who said, if you open up the motor and find the tails of the three coils, disconnect them from each other, then using a test meter to determine which is the opposite end of each coil. I did this and hey presto, I found them and separated them and connected wires to them. So I now have 6 wires U1 U2 V1 V2 W1 W2. I then reconfigured them so that U1 connected to W2, V1 connected to U2 and W1 connected to V2.. I connected live to U1, neutral to V1 and connected U1 and W1 together with a start/run capacitor.( makes it run clockwise)
    Plugged it in and it runs sweet..BUT it gets hot very quickly as in almost too hot to touch after 5 mins of no load use. This cant be right?
    I have used 2 different uF start/run capacitors , 30uF and 80Uf, and I have also wired the two in parallel to get 110uF but no change.
    Do I need more uF or does this need to be wired in a different way as in with separate start and a run capacitors.
     
  2. flameport

    flameport

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    Although some 3ph motors can be made to work on 1p just using a capacitor, it will be grossly inefficient and not suitable for any real use.

    Options are either buy a phase converter, a VFD, or a new single phase motor.
     
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  4. conny

    conny

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    As Flameport says, running it on single phase is highly inefficient and is likely to burn it out quite quickly.
    When it says it can run at 240v delta it means using 3 phases of a three phase supply or using phase converters etc. Without the correct control equipment you will be flogging a dead horse. Literally.
     
  5. Robert Peel

    Robert Peel

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    I think I've just found a 240v version of my motor. Just waiting for the seller to provide measurements to see if its going to be a straight swap, if it is I will be purchasing it as its about the same cost as a cheap Chinese vfd.
    Thanks for both your replies.
     
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