I learned I have 3 phase "high leg" at my new location, and need help using it

rdhem2 said:
Mr. hasler, shall we try again? You guys are so close yet so far away. Forget the neutral when wiring motors. Motor does not use it, does not care. Motor name plate says 208/240v it can be wired either 208v WYE or 240v DELTA connected transformer.
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That's what I said: The motor does not care how the transformer is wired: just what the line to line voltage is. I also noted that I knew of no three phase motors that made any use of the neutral.
 
Russ has it pretty much covered, not much to add except for some clarification, the primary reason for 208 wye to exist is to provide 120V circuits from a three phase wye leg to the center of the wye (neutral).

208V / 1.7320508 (the square root of 3) = 120V

I think this might be the "lightbulb" moment for the non electrically inclined.
 
I seem to remember 240 across the outer legs and 240 from each outer to the center. The outers each read 120 to neutral and the center read 240 to neutral. Does this sound like a high (or hot?) leg? Going from memory from looking at it this weekend so I could be wrong somewhere. The 220/440 motor has 6 windings, right now 3 are parallel.
 
Yes that sounds like High leg Delta from your description. Russ has already given you all the details so I won't reiterate it. His thoughts on a separate panel for the "single phase" loads is the only way we can do high leg Delta here. Three phase loads in one panel and all single phase (240 and 120) in another panel. Just bring the two hot wires that are 120V to neutral and the neutral into that panel.
Connect your 3 phase motor out of the 3 phase panel with one of the 3 hots to each leg of the motor and your motor will be very happy.
 
Mr. John Hasler. By singling you out, I was trying to get the point across that you were indeed the closest to the truth or closest to the way it works and can be used. NOT that you were in error!
 
Yes we do have a separate panel for the "regular" stuff. Thanks a bunch guys, here is the little Italian baby I am going to wire first with the 3 phase. Its a combination stone surfacer, single point HSS/CBN surfacer, and flywheel grinder (once I can find that attachment) Think of a bed mill with a really wide powered X travel and single speed 13" diameter cutting head and thats basically it. Now with this 3 phase knowledge I can open my options on a larger lathe than I was originally thinking too.
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for years one of the shops i worked at had a 110 plug hidden behind a cabinet..we moved everything around one day..first thing one of the guys does is plug in his radio..poof..turns out it was hooked to the wild wire . apparently no one ever used it since the place opened.
 
One last question (I hope) I found I have a run of 4 conductor wire that stopped about 5' short of the machine and was terminated, it must have been the original 3 phase install by the prior tenants. Its 12AWG solid. I found a calculator online and 208V with 7HP (cushion factor) calls out for 22A and 14AWG minimum. Would the electicians here feel comfortable direct connecting to this, it would be a total 45 foot run end to end, the last 7' feet is a flex 10AWG cable that was already on the machine.
 
5 hp at 230V would need at minimum #12. 7.5 hp at 230 volt would need #10. Your circuit should be OK, but without actually seeing the nameplate I couldn't say for sure. If you have a 20 amp breaker on the #12 in the panel where it is fed from you should have no problem. I assume that the machine has starters with overload protection built into it. Another issue that you haven't mentioned is how far the panel is from the machine for voltage drop. If I were running this circuit in new for you I would use #10. It's cheap insurance against any voltage drop issues. All that said it should run on the #12.
 
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