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Simple but clever motor wiring

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Pete.:
I have this little 3 phase motor that I took out of an automatic barrier. The barrier runs on single phase but I couldn't work out at first why the use of a 3-phase motor and capacitor, then it dawned on me. I knew that you can run a 3-phase motor on single phase by putting a capacitor to the spare leg but these guys have gone a step further and configured it so that powering one leg of the capacitor for forward (barrier up) and the other for reverse (down). Similar to reversing two of the three phase supplies on a 3-phase motor for reversing.

I thought I'd post here just for interest.

awemawson:
A nice bit of lateral thinking.

Thanks for sharing  :thumbup:

Arbalist:
Interesting, thanks for the picture.

I read some time back that it is not at all uncommon for manufacturers to fit three phase motors in products intended for use on a single phase supply, a simple capacitor being all that's required for operation. The reason given was the low cost and availability of electric motors on the open market.

I ran my three phase mill on single phase with just a large capacitor for several years without issue.

Will_D:
So just to be totally clear:

Am I correct: Grey is the Neutral and either Brown or Black is the live (depending on direction you want)?

DavidA:
Arbalist,

The only real problem with that approach is that the efficiency depends upon the capacitor being reasonably close to the ideal for the load.

Running a three phase motor on a single phase supply with a badly matched capacitor will result in the motor overheating.

It's quite easy to work out the correct value; as long as you know the load.

Dave.

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