Single Phase or Two Phase to Three Phase??

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cgardner1

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Is it possible to produce 3 phase from single phase or two phase incoming? I was told I would be able to provide 3 phase power to a motor from incoming high leg power.

Reason being is that installed breaker panel has breakers installed that skips b phase however I was told that I could use A and C on one side and attach wire other opposite side’s B phase.

Is it possible? And is it safe?


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"High-leg delta" aka 240/120v 3p4w service (lots of threads in the forums about that); that measures as 240v phase to phase but either 120v or 208v phase to neutral. If you have that, 240v single phase loads go only between the A and C phases (120v to N) and the B is only used for real 3-phase loads that can work with a delta feed (not everything can).

Make sense?
(I'll pretty much guarentee that you don't have real "two-phase".)
 
Makes sense, therefore it is single phase incoming? and 3 phase load cannot/should not be connected to it?


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cgardner1 said:
Is it possible to produce 3 phase from single phase or two phase incoming? I was told I would be able to provide 3 phase power to a motor from incoming high leg power.
Click to expand...
Not without some extra equipment like a phase converter or a VFD
cgardner1 said:
Reason being is that installed breaker panel has breakers installed that skips b phase however I was told that I could use A and C on one side and attach wire other opposite side’s B phase.

Is it possible? And is it safe?


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Click to expand...
Not sure what you mean by this. Do you have 3 phase power at the panel? If so, you could hook up a 3 phase load to A,B,C anywhere in the panel but it would not be safe because of the possibility of single phasing the load or not because you would need to turn off multiple breakers to kill power to the load.
 
L1 to N - 125V
L2 to N - 218V
L3 to N - 125V

Phase A to B 256V
Phase B to C 258V
Phase A to C 256V


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zbang said:
"High-leg delta" aka 240/120v 3p4w service (lots of threads in the forums about that); that measures as 240v phase to phase but either 120v or 208v phase to neutral. If you have that, 240v single phase loads go only between the A and C phases (120v to N) and the B is only used for real 3-phase loads that can work with a delta feed (not everything can).
Click to expand...
For 240V 2 wire loads, wouldn't that depend on the relative sizes of the supplying transformers? If they are sized for predominantly 3 phase loads, then I would think you'd want to spread the 240V 2 wire loads out evenly among the 3 possible pairs of phases. But if they are sized predominantly for 120V/240V loads, with only a small 3 phase capacity, then you'd want them all on A-C.

Or are there 240V 2 wire loads that expect the ungrounded to EGC voltage to be no more than 120V?

Cheers, Wayne
 
@cgardner1
I know that no electrician knows everything and some only deal with one aspect of the trade. But I find it quite disturbing that you, being an electrician, didn't know that you had 3 PH power already. Are you sure you're not in over your head on this?
 
Little Bill said:
@cgardner1
I know that no electrician knows everything and some only deal with one aspect of the trade. But I find it quite disturbing that you, being an electrician, didn't know that you had 3 PH power already. Are you sure you're not in over your head on this?
Click to expand...

True 3 phase was the question I should have been more clear


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You had a thread a couple months back about this same panel

3 Phase 240 V Panel?

Hello, I have recently encountered a breaker panel that is giving results that are unfamiliar to me when measuring voltage. The panel appears to be a 3 phase panel, it has three lines entering the terminals at the top of breaker. When measuring voltage across each phase to ground (A,B,C)...
forums.mikeholt.com

From reading both these questions, I feel you should ask your supervisor or other experienced electrician to help you. I believe this is above your level of training at this point. I am closing this thread.
 
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