Phase Rotation

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wasasparky

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What is standard utility phase rotation? ABC = Counter-Clockwise (CCW)?

Motors actually turn clockwise (CW) on CCW utility?

Do phase rotation meters that say CW/CCW really refer to motor rotation vs utility phasing?

ABC=CCW=CW rotation of motor?

Sorry for the fragmented questions...

For you UPS guys. Does a UPS care about CW / CCW?
 
wasasparky said:
What is standard utility phase rotation?
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We don't have a standard for phase rotation. We do keep track of our phases for circuit balancing. We also look at the rotation when disconnecting a bank for whatever reason to make sure we have the same rotation when it is reconnected. :smile:
 
In reality (or at least in mine), phase rotation is basically arbitrary. It's a relative thing. What matters is relative rotation.
 
chris kennedy said:
How would rotation affect circuit balancing?
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I think what they are saying is they keep track of the rotation so if a customer or customers are heavily loaded on one phase, they can juggle the phases while keeping the same rotation, the only thing that I've seen that you can almost guarantee rotation on is generators, most come from the factory phased clockwise.
 
chris kennedy said:
How would rotation affect circuit balancing?
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What I said was, "We do keep track of our phases for circuit balancing." We know what phases we have and what the configuration is on every distribution line. If we to run a 1? line from a 3? line, we do not just tap on and run it. We will look at the loading on the 3? line and tap the lightest loaded phase. :)
 
iwire said:
Many do, particularly if the have bypass feeds ruining through them.
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Never had this be an issue before.
Funny the UPS output wouldn't just match the input.
No manufacturers literature (OMM or Install) that I have found specifically states a requirement for CW. Some kinda mention vaguely about an error signal you might get if the phasing is incorrect - but still don't say CW or CCW.

This is just something the manufacturer and/or service reps just take care of during install, since nothing is really specifically mentioned about it?
 
I got called out to a recently completed building the UPS Tech was supposed to be doing start up and the UPS would fault out immediately. The tech said swap the phases, I did and all was good. :smile:

The Tech was happy so I left, there could be more to it but nothing that I was told.
 
wasasparky said:
How do the utilities share a common grid? . .
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We will do a phase transition if necessary to match the rotation. We also have to synchronize the phases before closing in the connection. I do not know the details since my expertise is in distribution and not substation or transmission. :smile:
 
iwire said:
I got called out to a recently completed building the UPS Tech was supposed to be doing start up and the UPS would fault out immediately. The tech said swap the phases, I did and all was good. :smile:

The Tech was happy so I left, there could be more to it but nothing that I was told.
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Many electronic reverse phase/undervoltage protection devices are designed with a fixed rotation. If you supply the device with a different rotation it will "not like it" and trip. The only solution is to swap the leads going to the device.
 
wasasparky said:
What is standard utility phase rotation? ABC = Counter-Clockwise (CCW)?
Click to expand...
No standard, it is what it is. ABC would be a likely choice, but some really big utilities, such as PG&E in Northern California, are ACB.

Motors actually turn clockwise (CW) on CCW utility?
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??? Motors don't "know" what direction to turn until you give them power. They turn in the direction of the rotation given to them. If you don't like it, swap any 2 leads.

Do phase rotation meters that say CW/CCW really refer to motor rotation vs utility phasing?
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They are based on the power applied to them, just like the motors. See above.

ABC=CCW=CW rotation of motor?
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Same issue, I guess.


For you UPS guys. Does a UPS care about CW / CCW?
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Answered by others, but I'll add a bit more. It's because of the bypass circuits. A double conversion UPS creates the output as if it is a new source, so from that standpoint they couldn't care less what the input phasing is. It takes in AC, converts it to DC, then recreates the AC. If the AC fails, it uses the batteries as the source for DC, never even hiccups. But many have a bypass circuit to provide for instantaneous peak loads such as transformer inrush etc. They therefore force you to conform to what their output phasing is, that way if it goes into bypass, you don't have things running backwards. You could technically take care of that on your own, and in fact that is the situation with bypass circuits on VFDs (same issue), but I guess because UPSs are usually on very high profile equipment, they don't want to take chances.
 
wasasparky said:
Never had this be an issue before.
Funny the UPS output wouldn't just match the input.
Click to expand...
Even if it didn't matter to the UPS, it might matter to it's connected load.
 
The correct terminology is "the order in which the phases reach the positive maximum"

Further, just because you have the rotation correct, doesn't mean two (or more) sources are in phase. The angle also has to be correct. Remember when your talking about voltages, e,g, 4160V, 480V 208V, etc. you are only talking about magnitude. These are complex numbers which have magnitude (voltage) and direction (angle).

A simplistic example is looking to see what happens to a voltage as it goes through a delta/wye transformer. There is a 30 deg phase shift, IEEE std is HV lead LV by 30 deg, but you can specify others. Take two sources, both fed from the same substation. One source goes from the substation at 13.8kV and steps down to 4160V, then another transformer steps it down from 4160V to 480V. The second feeder goes from 13.8KV down to 480V directly. Both sources are at 480V but because of the transformers they are 30 degrees apart at the 480V bus, and therefore cannot be paralleled, even though the rotation is the same.

This is why on jobs, with multiple transformers, any interconnection or desire for parallel operation (even momentary) needs to be carefully analyzed. Typically, a 3-line phasing diagram is required.
 
Jraef said:
...A double conversion UPS creates the output as if it is a new source, so from that standpoint they couldn't care less what the input phasing is.
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Yes, and it appears when it creates the new source, it does so in a clockwise fashion, regardless of the input's orientation.

They don't care what the phasing is beacuse the UPS checks for sync and will inhibit a transfer to bypass. The UPS still works, until it needs to go to bypass, but can't.

I fully understand the issue, but am surprised that such an important requirement is hard to find (if at all) in UPS product data, install, OMM's, etc.
 
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