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Thread: 3 phase : rotation of motor.

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  1. #1
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    3 phase : rotation of motor.

    Donkey's years ago if you wanted to change which direction a 3 phase electric motor ran you just swapped two of the live wires over (after switching everything off obviously !) Can anyone tell me if that is still the case please ? TIA for any advice/help.

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    Senior Member Footsfitter's Avatar
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    Re: 3 phase : rotation of motor.

    Yes, just swap over any two of the three live conductors (usually done in the motor's terminal box) which will reverse the rotation.
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    Re: 3 phase : rotation of motor.

    Quote Originally Posted by Footsfitter View Post
    Yes, just swap over any two of the three live conductors (usually done in the motor's terminal box) which will reverse the rotation.
    Thanks Peter. Was hoping you would come up with a reply.

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    Senior Member 4wd's Avatar
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    Re: 3 phase : rotation of motor.

    From York Machinery auctions we have acquired a used - probably 1970s - metal cutting band saw *thing* it is very industrial and heavy duty from some foundry most likely.
    It has a three phase motor, but only have single phase here.
    We knew this and a relation is knowledgeable and qualified in electrickery - and speaks of a converter box(?)
    Or would it be a better option to fit a single phase motor ...
    Having had a quick look under guards etc there's a lot of still bright filings accumulated it must have been in regular use until very few weeks/months ago.

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    Senior Member Footsfitter's Avatar
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    Re: 3 phase : rotation of motor.

    Not played with a phase converter, but IIRC they came in 2 styles, old way was through a motor type converter I think. More common way with the advent of sheeps-guts or rather electronics are modern phase converters and all I know is that you have to be very aware of matching up the right size motor to converter?

    Another IIRC- doesn't going single phase bring the penalty of a much larger motor to get the power/torque?
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    Senior Member 4wd's Avatar
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    Re: 3 phase : rotation of motor.

    I think it's only rated at one horsepower and the 3 phase fitted does look surprisingly small, I think it is primarily driving a hydraulic pump.
    I'm guessing something similar to what's fitted on our 6" grain augers would be overkill - they are very heavy mind.
    It probably isn't especially demanding in torque but must say at the moment I am somewhat hazy about how it works, it can saw through RSJs up to about 18" by the look of it.

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