I need some help wiring a 3-phase 240 volt motor in my shop.?

Question

The electric panel has 4 wires coming in...three are "hot" and one is the ground. On my wiggy, it reads 240 volts phase to phase and 120 volts phase to neutral and ground. How (if I can) do I connect to a 3-phase 240 volt motor?

Answer 1

Something doesn't compute. You cannot have 240V between any 2 phases of a 3 phase system AND have 120V phase to ground (for all 3 phases).

If you are wiring to your panel, there is a lot more information needed to get the right wire and breaker size. Perhaps you should have an electrician do this.

You are sure you have 3 phase? 4 wires could be 2 hot, neutral, and ground. You mention neutral and ground, but only 1 wire coming in. If this is the service panel, the wire coming in is a neutral and not a ground. I ask this because I wouldn't expect 3 phase for residential, and I wouldn't expect someone who doesn't know what they are doing working on a commercial panel.

Answer 2

I'm thinking like "an electrician" in the previous answer

It doesn't sound like a 3-phase motor?

You didn't smuggle it home from the factory did you?

Small motors like that would much more likely be a single phase 240V

In residential wiring you get the 240V by using the two, out of phase, 120 V sources that homes are wired with.

You probably need a book (or an electrician) to help you do this the first time. In your electrical box their should be two busses and they are arranged so that circuits next to each other are supplied from the different buss

A "240V breaker" covers two spots and thus both busses. Wired correctly, the 240V is developed "phase to phase" like your nameplate said. (-120 to +120 is 240, the two phases alternate oppositely)

Lots of time motors like that can be wired 240 or 120.

Don't do anything until you know precisely what you have there!
Then get an electrician or at least a book for some help.

Answer 3

It sounds as if you have a 'Y' feed with the center leg being frame (or earth) ground. The motor should have 3 leads coming out of it (and, possibly, a frame ground line) and these will tie to the three 'hot' lines in the distribution panel. The ground should be tied to the metal frame of the motor (or to whatever the motor is mounted to). If the motor has a frame ground line, tie it to that.

Note that a 3-phase motor can run in either direction. Make sure you determine what the 'correct' direction is for the motor and check it after you've tied it up. If it's running 'backwards, just swap any 2 of the hot lines going to the motor.


Doug

Answer 4

The four wires comming in are designated as R, Y, B (hot) and Neutral. For a three phase motor, you do not have to connect Neutral.

Some motors (depending on the rating) will have either a terminal box or wires comming out.

If your motor has a terminal box, there will be six terminals arranged in two rows. They will be labelled as U1, V1, W1 and U2, V2 and W2.

Shorting links will be provided in the terminal box. You can short either U1, V1 and W1 or U2, V2 and W2 and connect the unshorted ends to R, Y and B via a starter or MCB.

If your motor has loose wires, there will be either three wires or six wires (one end of each coil - a three phase motor has three sets of windings - one for each phase )

If it is three wire, connect the wires to R, Y and B via a DOL (Direct On Line) starter or MCB (Miniature Circuit Breaker) of proper rating.

If it is six wires, find one end of each coil and short them together. Then connect the other three to R, Y and B as above via a starter.

The above advice holds true only if your motor is less than 5 HP (3.7 KW). If it is above that rating, then u have to go in for a star delta starter, in which case, all the wires have to connected in a particular fashion, needless to say, a professional electrician's job.

If you have arrived this far, and find that the motor is rotating in the opposite direction, then interchange any two hot leads, R and Y or Y and B.

Good luck.

Answer 5

is your shop 3 phase? if not you need a freak drive or build a convertor out of another motor and capasitors. also there is different kinds of 3 phase