# How do you know ABC?



## Rap2 (Dec 17, 2010)

How can you verify phase A, B and C are marked correct by the utility?

The only experience I have with phasing is that when a 3 phase motor is wired ABC, BCA or CAB it spins one direction and if its wired CBA, BAC or ACB it spins the other, therefor if you swap any 2 leads it will spin the other direction.

I recently hooked up 2 three phase solar inverts according to to the phasing as identified by the utility, both were wired ABC.

When we switched on the inverts they both gave a fault indicating the phasing was wrong. So i figured swap any 2 legs and the order will be correct.

On the first inverter I swapped A and B, but on the second one I couldn't get the lug loose on A so I swapped B and C.

Much to my surprise the first inverter worked and the other still had the fault. 

I put back B and C on the inverter and swapped A and B at the disconnect and now they both work.

Obviously the inverter needs to be hooked up ABC and although BCA and CAB are the same sequence it does not work.

I have seen tools to check rotation of motors but don't know of a way to define A from B from C.

Thanks for reading my question, and for any response.


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## B4T (Feb 10, 2009)

Was this a 120/208 wye or a delta service.. 

The high leg is the only thing I can see that would give you troubles..

I have never had that problem.. but I always check it falls on the same lug..


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## BBQ (Nov 16, 2010)

I agree with B4T, I don;t believe there is any device that can actually tell A from B from C. All you can find is the rotation.


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## chicken steve (Mar 22, 2011)

http://www.youtube.com/watch?feature=player_detailpage&v=d6tlZzkqfHw


~CS~


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## Rap2 (Dec 17, 2010)

It comes in via 12 or 23 kv service to a transformer as a delta and comes out 480 wye.

It does not have a high leg to my knowledge but I will check next time I go out there.

Any other reason why swapping B and C didn't work and swapping A and B did?


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## kaboler (Dec 1, 2010)

I can't figure it out. Poor me. What a riddle!


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## chicken steve (Mar 22, 2011)

Rap,
perhaps the solar inverter manufacturer has tech support?

~CS~


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## Rap2 (Dec 17, 2010)

Wires swapped or miss taped did not matter (and I checked), I turned it on and it did not work, I swapped B and C and it did not work. (according to the same error and the fact that it did not turn on), I then put B and C back and swapped A and B and it did work.

Swapping 2 wires was the fix but it had to be the right 2, not any 2.


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## Rap2 (Dec 17, 2010)

I will call the manufacture just to get an answer.... and I will check to see if there is a high leg... though the building is kinda new and do not believe it is set up that way.


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## den (Mar 28, 2009)

Don't know about your inverters but on our dist system that I worked for, b phase never left the middle. a and c we traced out and on 2 way feeds we would check phasing with a high voltage volt meter to get things in sync with each other. can you get to a known source for referance and then volt check for phasing.


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## 76nemo (Aug 13, 2008)

BBQ said:


> I agree with B4T, I don;t believe there is any device that can actually tell A from B from C. All you can find is the rotation.


 
What the h*ll else would you need to find???????

This is interesting..........


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## A Little Short (Nov 11, 2010)

B4T said:


> Was this a 120/208 wye or a delta service..
> 
> The high leg is the only thing I can see that would give you troubles..
> 
> I have never had that problem.. but I always check it falls on the same lug..


A high leg wouldn't cause a problem. In a 3 pf system, it doesn't see a high leg when going Ph to Ph, only ph to neutral/ground.


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## Rap2 (Dec 17, 2010)

den said:


> Don't know about your inverters but on our dist system that I worked for, b phase never left the middle. a and c we traced out and on 2 way feeds we would check phasing with a high voltage volt meter to get things in sync with each other. can you get to a known source for referance and then volt check for phasing.


This whole business park is underground wiring, the only reference I would have using a volt meter as you suggest would be if the utility (or who ever hooked up the service) got it rite.


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## Rap2 (Dec 17, 2010)

chicken steve said:


> http://www.youtube.com/watch?feature=player_detailpage&v=d6tlZzkqfHw
> 
> 
> ~CS~


MJ may know ABC but it tuns out it my not be as easy as 123......


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## B4T (Feb 10, 2009)

Little-Lectric said:


> A high leg wouldn't cause a problem. In a 3 pf system, it doesn't see a high leg when going Ph to Ph, only ph to neutral/ground.


I don't know if it would or not with new motors.. but what about something (30) years old?

It is just a habit of making sure when ever I am working with a high leg..

If something does not work right like in the OP.. it is one less thing to check..

When troubleshooting you have to think outside the box.. IMO..


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## BBQ (Nov 16, 2010)

B4T said:


> I don't know if it would or not with new motors.. but what about something (30) years old?


New old it does not mater, any straight three phase load will not care about a highleg.



> When troubleshooting you have to think outside the box.. IMO..


I agree, and I think your idea about a highleg was a good one. (An idea that would not have come to me as I rarely run into highlegs)

This inverter may use a neutral (some do, some don't) or it may make measurements from hot to ground, either way in that case a high leg could be a problem.


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## A Little Short (Nov 11, 2010)

B4T said:


> I don't know if it would or not with new motors.. but what about something (30) years old?
> 
> It is just a habit of making sure when ever I am working with a high leg..
> 
> ...


I don't know anything about 3 ph solar inverters. I was only going by the 3 pf part. Any 3 ph motor or purely 3 ph system *not* using a neutral will not see the high leg.


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## BBQ (Nov 16, 2010)

Little-Lectric said:


> I don't know anything about 3 ph solar inverters. I was only going by the 3 pf part. Any 3 ph motor or purely 3 ph system *not* using a neutral will not see the high leg.


I agree with you 100%, I just don't know if the inverter is purely 3 phase or takes measurements to ground or neutral. I suspect it would.


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## 76nemo (Aug 13, 2008)

I am baffled here. This does NOT add up by any means whatsoever.


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## B4T (Feb 10, 2009)

76nemo said:


> I am baffled here. This does NOT add up by any means whatsoever.


What don't you understand.. :blink::blink:


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## 76nemo (Aug 13, 2008)

B4T said:


> What don't you understand.. :blink::blink:


I don't know why the good guys finish out last:001_huh:

Just kidding, how ya doing Bob?

I read this a few times. From what Rap2 reports, this makes no sense at all. He states that only swapping two individual legs makes a difference. I can't wrap my head around this. If the rotation is correct, the order doesn't make a difference. I have never seen it, and couldn't even begin to design a circuit in which it could.

This morning I'm thinking "I can't wait to hear what tech support has to say". The more I thought about it, the more I scratched my tail.

I'm lost, I can't even help or don't have a thing to offer. It just doesn't add up......


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## kaboler (Dec 1, 2010)

My journeyman said today that it can happen, and he doesn't know why, and there shouldn't be a reason for it.


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## jefft110 (Jul 7, 2010)

To the OP:

Are you positive that you actually swapped two phases the 1st go around, or just think you did?

In other words, do you think it's possible that you may have connected them back the way you took them off?

I know that sounds too simple a mistake, but I've caught myself making that same mistake in a rush/distracted before.


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## Rap2 (Dec 17, 2010)

It turns out it was a series of events that had nothing to do with phasing.

The error was a "Phase Error" but the only explanation in the manual for that code was to "call the manufacture"(who was closed). The error was actually reporting a phase imbalance which was outside if its operating parameters and shutting down the system.

It so happens we rolled up right around quitting time and when we did the phase swap the first time, one of the systems had some of the loads shut off and was operating fine and had nothing to do with me swapping A and B phases.

The second inverter had its imbalanced loads turned off by the time I got around to putting back the B and C phases and swapping the A and B phases for it on the disconnect and they both worked for the rest of the day till the sun went down. which was a few hours.

The next day both were back in fault, I called the manufacture and the told me how to increase the imbalance threshold.

I then inquired about phasing and was told this particular inverter did not care about phase rotation and could be hooked up any way you want.

Sorry for the confusion, this one really had us going from what seemed to be happening.

I have to now go back out there and put all the wires the way they were and check into the load imbalance on the 2 systems.


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## HARRY304E (Sep 15, 2010)

Rap2 said:


> It turns out it was a series of events that had nothing to do with phasing.
> 
> The error was a "Phase Error" but the only explanation in the manual for that code was to "call the manufacture"(who was closed). The error was actually reporting a phase imbalance which was outside if its operating parameters and shutting down the system.
> 
> ...


If you guys do not have a phase rotation meter here is a good one...


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## kaboler (Dec 1, 2010)

dang harry, 130 to find out if the phases are reversed? Isn't that a big waste of money?


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## oldtimer (Jun 10, 2010)

kaboler said:


> dang harry, 130 to find out if the phases are reversed? Isn't that a big waste of money?



The first time you connect a motor with the rotation reversed, and demolish a bunch of equipment, you will wish you had used a rotation meter!

Guessing can be costly!

Do you feel lucky???


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## 76nemo (Aug 13, 2008)

kaboler said:


> dang harry, 130 to find out if the phases are reversed? Isn't that a big waste of money?


 

:001_huh::blink::001_huh:


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## HARRY304E (Sep 15, 2010)

kaboler said:


> dang harry, 130 to find out if the phases are reversed? Isn't that a big waste of money?


In fact it is if you have no clue..:blink:


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## 76nemo (Aug 13, 2008)

kaboler said:


> My journeyman said today that it can happen, and he doesn't know why, and there shouldn't be a reason for it.


 
I'd like to witness it............

I think he's confused.


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## HARRY304E (Sep 15, 2010)

76nemo said:


> I'd like to witness it............
> 
> I think he's confused.


I think he was on a roll early this morning...:laughing:


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## Rap2 (Dec 17, 2010)

what made this particularly frustrating is that after myself and another electrician insisted to our foreman that it didn't matter which 2 phases we swapped to change rotation, he insisted that swapping A and B fixed one and that we should put back B and C and swap A and B elsewhere to fix the other.

We argued that that would not help and that he did not understand the problem. I only swapped A and B in another location to pacify our foreman.....

We were chewing on some serious crow when it appeared that he was right..

He was ribbing us about it the next day till we rolled up and found both inverters back in error....


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## HARRY304E (Sep 15, 2010)

Rap2 said:


> what made this particularly frustrating is that after myself and another electrician insisted to our foreman that it didn't matter which 2 phases we swapped to change rotation, he insisted that swapping A and B fixed one and that we should put back B and C and swap A and B elsewhere to fix the other.
> 
> We argued that that would not help and that he did not understand the problem. I only swapped A and B in another location to pacify our foreman.....
> 
> ...


Well it really does not matter which phases you swap as long as just swap 2 of 3.


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## 76nemo (Aug 13, 2008)

Rap2 said:


> what made this particularly frustrating is that after myself and another electrician insisted to our foreman that it didn't matter which 2 phases we swapped to change rotation, he insisted that swapping A and B fixed one and that we should put back B and C and swap A and B elsewhere to fix the other.
> 
> We argued that that would not help and that he did not understand the problem. I only swapped A and B in another location to pacify our foreman.....
> 
> ...


 
Gotta love those moments:laughing:

"Put that one in your pipe and smoke it".:icon_redface:, but hey, you're not paying him:whistling2:


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## Lone Crapshooter (Nov 8, 2008)

When we pull in a circuit to a tie switch we will lock open the tie switch and energize the 2 feeds . Then with a meter or phasing sticks depending on the voltage we will measure the voltage across the open switch.
if it is correct it should look this.

1 A to 2 A 0
1 A to 2 B high voltage
1 A to 2 C high voltage

1 B to 2 A high voltage
1 B to 2 B 0 
1 B to 2 C high voltage

1 C to 2 A high voltage
1 C to 2 B high voltage
1 C to 2 C 0


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## brian john (Mar 11, 2007)

To verify utility to a customers system we use to meters preferable analog. Place the one meter across “A” phase utility and “A” phase inverter, Place the other meter across “B” or “C” phase utility and the matching phase inverter. 

Do the inverters have utility tracking to try to keep in phase with the utility, if so the above method will work.


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## Rap2 (Dec 17, 2010)

Lone Crapshooter said:


> When we pull in a circuit to a tie switch we will lock open the tie switch and energize the 2 feeds . Then with a meter or phasing sticks depending on the voltage we will measure the voltage across the open switch.
> if it is correct it should look this.
> 
> 1 A to 2 A 0
> ...


I get it, that would totally work for matching the phases to each other from the same sign generating source. Im not totally sure that if you were hooking in a separate sign generating source that A to A would be 0 volts every time, if each independent generating source were slightly out of phase with each other you may get potential from A to A, B to B, C to C even when hooked up right, which could be adjusted to 0 if you had control over one of the generating sources. 

I will probably never hook up a such a system because all PV inverters (to my knowledge) do not generate a sign wave, they sync to the one coming in from the utility, and when it goes away they shut down. 

Yea I know off grid systems generate a sign wave, however even those in a high bread situation do not generate a sign wave when hooked to the grid they only sync.. when the power goes out the disconnect from the grid and generate a sign wave from whatever DC source they have but only on the customer side of the circuit, exactly the way a UPS would and switch back to grid sync when the power comes back on from the utility.


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## Rap2 (Dec 17, 2010)

brian john said:


> To verify utility to a customers system we use to meters preferable analog. Place the one meter across “A” phase utility and “A” phase inverter, Place the other meter across “B” or “C” phase utility and the matching phase inverter.
> 
> Do the inverters have utility tracking to try to keep in phase with the utility, if so the above method will work.


What kind of inverters are these? Do they generate their own sign wave when not hooked to the utility, what happens if you get a slight reading between the phases even when they are hooked up correctly, can you adjust it out in some way I am not familiar with systems that utility track after the fact ??

Yes every inverter I have ever hooded up has utility tracking to sync to the grid however due to anti islanding requirements it will not turn on until it can sync with the utility, hence the method wont work across an open switch.


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## brian john (Mar 11, 2007)

Rap2 said:


> What kind of inverters are these? Do they generate their own sign wave when not hooked to the utility, what happens if you get a slight reading between the phases even when they are hooked up correctly, can you adjust it out in some way I am not familiar with systems that utility track after the fact ??
> 
> Yes every inverter I have ever hooded up has utility tracking to sync to the grid however due to anti islanding requirements it will not turn on until it can sync with the utility, hence the method wont work across an open switch.


UPS systems track the utility when the utility is off the UPS operate independently but remain close as the 60 HZ is tight, when the utility returns they ups operates to track and sync.

With generators the speed is adjustable and older UPS’s you could do fine tune, but newer systems do this automatically.


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## millelec (Nov 20, 2010)

kaboler said:


> dang harry, 130 to find out if the phases are reversed? Isn't that a big waste of money?


try paralleling a 3 phase generator that has phases reversed as well. never saw it done, have heard stories of the results.


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## Rap2 (Dec 17, 2010)

millelec said:


> try paralleling a 3 phase generator that has phases reversed as well. never saw it done, have heard stories of the results.


You will be visited by Mr. Archy Sparky who is always up for a good time!!!:thumbsup:


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## varmit (Apr 19, 2009)

The solar system probably has a processor with phase matching firmware, in order to be able to be in sync with the utility phasing. Otherwise, you would have a real problem trying to feed back to the utility- smoke and loud noises.
This synchronization function happens at all power plants before the generator is connected to the power grid.


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## Rap2 (Dec 17, 2010)

varmit said:


> The solar system probably has a processor with phase matching firmware, in order to be able to be in sync with the utility phasing. Otherwise, you would have a real problem trying to feed back to the utility- smoke and loud noises.
> This synchronization function happens at all power plants before the generator is connected to the power grid.


Yes but this happens internally and you would never have power at an external switch that is in the off position in order to preform the fore mentioned test between phases across the open circuit.


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## brian john (Mar 11, 2007)

millelec said:


> try paralleling a 3 phase generator that has phases reversed as well. never saw it done, have heard stories of the results.


I have seen two 500 KW motor generators try to parallel out of phase one of the motor generators literally jumped. And the repair required more than swapping tow phases. Also was on a site where they paralleled a 750 MG with the utility out of phase, the utility won that battle.


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## brian john (Mar 11, 2007)

Rap2 said:


> Yes but this happens internally and you would never have power at an external switch that is in the off position in order to preform the fore mentioned test between phases across the open circuit.


And that is where you use your meters.


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## BBQ (Nov 16, 2010)

varmit said:


> The solar system probably has a processor with phase matching firmware, in order to be able to be in sync with the utility phasing. Otherwise, you would have a real problem trying to feed back to the utility- smoke and loud noises.
> This synchronization function happens at all power plants before the generator is connected to the power grid.


Of course it has to sync but it does not know and cannot tell phase A from phase B, it can only determine the rotation.


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## Rap2 (Dec 17, 2010)

brian john said:


> And that is where you use your meters.


the machine comes on and energizes its internal circuit for a few seconds as apart of a power up cycle, if it does not see power from the utility or it can not sync it turns off, but yes you are correct, you would have to get into the software and tell it not to turn off or connect to grid at which point you could take the reading.


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## kaboler (Dec 1, 2010)

oldtimer said:


> The first time you connect a motor with the rotation reversed, and demolish a bunch of equipment, you will wish you had used a rotation meter!
> 
> Guessing can be costly!
> 
> Do you feel lucky???


Good point.


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## Rap2 (Dec 17, 2010)

Another interesting thing is that unlike other inverters this inverter did not care about phase rotation, not sure how it does it but you can put the 3 wires any way you want and it will work. (I guess since its making power from DC it can pick the rotation it wants based on how it tests the AC line)

Most inverters you hook up to 3 phase in fact don't have all three phases. They are 2 pole inverters that sync to any 2 hots and if you don't want unbalanced production you will need a minimum of 3 separate inverters which you have to physically interleave among the phases 2 poles at a time (AB BC AC).


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## Lone Crapshooter (Nov 8, 2008)

This might be too much to late but what about a sync check relay in a permissive circuit with a electrically operated circuit breaker or contactor.When your inverter is in sync with the utility the sync check will let the breaker or contactor close in on the utility. 

The old fashon way is with light bulbs across the breaker when the bulbs are on out of sync bulbs off in sync . Some times you see that arrangement plus a sync scope.


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