120deg out of Phase?

[champion]

Is it unusual for a utility company to not know which primary phase is A, B, C.
Primary line voltage in this project is 2400v.
The connection will be for 208v 3 ph service.
I noticed that the connection on the load side of the meter to the main disconnect is not the same.
Example---PHASE A = RED, PHASE B = YELLOW, PHASE C = BLUE ON THE LOAD SIDE OF THE METER.

These cables terminate on the disconnect as follows:
PHASE A = BLUE, PHASE B = YELLOW, PHASE C = RED.

Assuming that the utility company will connect the main transformers phase A, B and C to the appropriate cables as the meter is wired, I don't really have a problem.
When I asked the utility company to be sure and connect these phases to match the meter connections, they told me that they don't really know for sure which primary voltage is phase A, B AND C. They just connect them like they always do and nobody has any trouble.
I was thinking of getting my scope out and determine which phase is which for them but maybe its not just that necessary.
I was concerned about this a bit regarding the 3 ph A/C units installed on the roof of this building.
As far as load balancing on this project----I don't really think a big effect will be caused because of it, but I was shocked to hear what I heard.

Any input---

Thanks
Jim

 

[iwire]

Re: 120deg out of Phase?

Phase A is whichever one you chose to be phase A.

How would a scope determine which phase is A?

 

[ron]

Re: 120deg out of Phase?

The only thing you need to worry about is phase rotation, clockwise or counterclockwise. Once the utility makes the connection, be sure the rotation is the same throughout the facility. It is nice to be consistent throughout the facility regarding which phase is which after you are connected by the utility however they they do it. This is for load balancing and troubleshooting.

 

[caj1962]

Re: 120deg out of Phase?

How would 3 phase equipment ever cause an imbalance. And how would a scope meter tell me about it any better tham an amp meter? Just curious enough to ask.

 

[charlie b]

Re: 120deg out of Phase?

Originally posted by caj1962: How would 3 phase equipment ever cause an imbalance?

By being imbalanced internally. A single 3-phase motor is unlikely to draw an imbalanced load, but it is possible. You could get it from a manufacturing defect or from having very ?generous? manufacturing tolerances.

And how would a scope meter tell me about it any better than an amp meter?

A scope would show you the phase relationship between the three currents. An ammeter would only show you the magnitudes of the currents.