3 phase motor wiring?

Kramer

Just a quick question about wiring a 3 phase motor.

Supply is 4 wire, brown, blue, black & earth.

Motor has 4 cables, 3 black & an earth.

Does it matter which goes where, earth excepted? I assume there's 120v between each phase & each phase to earth?

Also, how can one reverse the rotation of the motor?

Couple of Qs actually .

TIA.

Michael Collins

All goods questions!

Does it matter which goes where, earth excepted?

It does indeed and this is actually related to your other question about direction of rotation

I assume there's 120v between each phase & each phase to earth?

Well in theory you could connect it to a supply rated anywhere within the specs of the motor, but if you're connecting it up to a standard ESB three phase supply here in Ireland there'll be 230 V r.m.s. between any phase and ground (earth) and about 400 r.m.s. V between each phase

Also, how can one reverse the rotation of the motor?

You can do this by swaping the A & C (R & T in the old format) phases as it's a rotating magnetic field that causes it to move and this just makes the field rotate the other way. The phases are normally colour coded but since the three motor phase wires are black you'll just have to use trial and error - it shouldn't damage the motor. But remember the voltages are very high so wear saftey mittens and use a round nose scissors!!

Kramer

Thanks for thr reply Michael.

I got it installed anyway & it's A-OK. It was actually bring run on a HUGE 3-phase generator.

Ran the right way so was easy enough.

Thanks again.