Electrical question~ 3 phase /220 single phase question

[Brian Weick]

A friend of mine just bought a 220vlt 3ph shaper with a 220v single phase power feed attached to the unit.

:confused:The diagram below represents what he has coming in. I think the 110v into the junction box is not part of the solution , so he is left with the 220 volt 3 phase.
1.)Can he get 220v single phase out of the three phase using the ground wire coming in ?

2.) If he does this, and this is what I am thinking , will he be reducing the amperage by running both off of the same line.

Personally, I don't think this is a good idea, even if it is feasible, to much on one line i would have to surmise.

let me know,
Thanks
Brian

[William Cummins]

If you have a grounded delta 240v 3 phase service, you will have a high leg on one of the phases. You can use the 2 non high leg phases to provide 240v to the feeder. If you mess up and attach the wild/high leg ( about 208v to ground ) to the feeder as one of the 2 hots you will fry it out.

If you have an wye 208 service you can use any of the hots to power the feeder. BUT, you might not provide enough voltage at 208V for the feeder ( and maybe the shaper main motor too) So if you have this service check the motor spec plate and see if the motor can run on 208v.

William...

[Brian Weick]

thanks ~ How do I check the voltage coming out of the legs ~ do I tap the - lead on the VM to the junction box and the hot + to one of the legs?

Thanks for your help William,:)
going there tomorrow to help him out with this.
Brian

[Rob Russell]

For your testing - yes.

If the color-coding in your diagram matches the wiring, I'd try the blue leg as the wild/high leg. If you had an orange conductor (vs. red), I'd suspect it first as the wild/high leg.

[Brian Weick]

Based on the information I was given by William~ I have to check the system first ~ to see what is what and then go from there. But I do use this in conjunction with the ground on the chassis ~ Correct? Isn't there a color code to 3 phase to verify the design of the electrical service ~when it comes to 3 phase and up~ it gets a little confusing. I have a few vfd's running 3 phase from single phase 220vlt, now I do"not" have the three phase grounded to the motor~ the 3 legs that come off of the VFD get connected to the wiring diagram of the motors that operate my machinery. I am just absolutely stumped~ one of those legs has to be a - , or neutral wire to complete the circuit~ correct, there is no"ground" coming from the VFD to the motors~ t1.t2.t3. terminals "only" where the heck is the neutral to complete the circuit, and if you have 3 phase into you shop~ how is this circuit being completed without the neutral~ something is missing from this situation that I do not , for the life of me, have yet explained to me, I only have the VF D's to convert to 3 phase so I am sure there is a different animal over at my friends shop, but what the heck is completing the circuit???????
Thanks Rob
Brian

[William Cummins]

Ok now we have 2 different things mixing tougher

The information I gave you was for a true 3 phase service, not a VFD. Are you running this on a VFD or a 3 phase service?

To test the service for the service voltage I would test between the hots of the 3 legs with a multimeter to figure out the voltage. IF it's 208 between phases then you can use any 2 of the hots to power your feeder. IF it's 240V between the phases then I would find an equipment ground ( and _only_ for the test) and use it to find the high leg between the hots and the equipment ground. ( I'm assuming that you don't have a grounded conductor [a neutral] at the plug in site) IF you have a 4 wire plug with an equipment ground ( five blades on the plug) Use the neutral to test the line to the grounded voltage.

William...

[Rob Russell]

3-phase motors don't have a "neutral", just as a 240v single-phase motor doesn't have a "neutral" either.

3-phase motors rotate because the magnetic field in the windings rotates around the motor. It's something about having that 3rd leg that does it. An electrical engineer could explain why, but I'm not an EE. That's why 3-phase motors don't have start capacitors and can generally be reversed by switching direction on 2 of the legs.

There are 2 types of 3-phase power - "Delta" and "Wye" or "Y". The power that comes off of a rotary phase convertor is Delta. Without going into a lot of detail, Delta 3-phase is where you will have the "wild" or "bastard" leg that's 208v to ground. That doesn't matter though - the motor would just see 240v/3-phase.

In terms of hooking up the motor - the thing you have to be careful about is control circuitry or accessories, like the power feeder. That's why you need to know if the individual voltage to ground on one of the 3 hot legs is 208v. You would ONLY use that "wild" leg as a feed to the motor. The other 2 hot legs should be 120v to ground and could be used for accessories and control circuits.

[Brian Weick]

First question:,William~ "Are you running this on a VFD or a 3 phase service?" ~ no~ I was just comparing what I have running at my shop compared to what is at my friends~ he has "mechanically wired" 3 phase at the shop~ all over the place.

So it is a hard wired ~ write from the Electric company 3 phase~ so If it is a Delta~ I use the "non bastard" wires and a ground to complete the 220 single phase , is it is the Wye , then I can can use any 2 of the 3 legs and the Junction box ground to get the 220vlts to the power feed?

Brian

[William Cummins]

Sounds like you have it. The ground is only an equipment/safety ground in a 3 phase motor application ( used to ground the motor frame so if there should be a short between the windings and the frame, you have a return path so the breaker will trip) and a grounded conductor ( the neutral) is not needed for a 3 phase motor application either.

William....

[Brian Weick]

thanks , you have been a great help~ thanks again William :)
Brian