Does phase 2 (black) always lag phase 1 (red) by 120, lead phase 1 by 120, or is it arbitrary. I have two motors connected to the same drive shaft with 1 motor flipped around so it needs opposite phase rotation. There is no phase correction circuit and I want to minimize rewiring in the field. Any help would be appreciated.
Standard Phase Rotation
- Thread starter mic
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Standard Phase Rotation
There is no code requirement related to matching a color code against a phase rotation pattern. In addition, there is always the possibility that any given feeder at any given facility might not follow the same pattern as another feeder at the same facility. Unless you have access to an oscilloscope or a meter that can tell you how phase rotation works at your facility, then you will have to go with a ?trial and success? method
(I?m trying to be optimistic).
There is no code requirement related to matching a color code against a phase rotation pattern. In addition, there is always the possibility that any given feeder at any given facility might not follow the same pattern as another feeder at the same facility. Unless you have access to an oscilloscope or a meter that can tell you how phase rotation works at your facility, then you will have to go with a ?trial and success? method
(I?m trying to be optimistic).stew
Senior Member
- Location
- federal way,washington
Re: Standard Phase Rotation
What do you mean by a phase adjustment circuit? all you really have to do is change two of the leads to one of the motors.Then you have one one way and the other the other way. Just change one motor in the motor conduit box.you need to have one cw and the other ccw. lets ay you start with black red blueon motor # 1. bump the load with one motor to see if the shaft rortates in the proper direction. If it does and you are coming off a common feed then connect the 2nd unit red black blue.If the first motor is not roataing correctly just go red black blue on #1 and black red blue on #2.
[ August 04, 2004, 12:50 AM: Message edited by: stew ]
What do you mean by a phase adjustment circuit? all you really have to do is change two of the leads to one of the motors.Then you have one one way and the other the other way. Just change one motor in the motor conduit box.you need to have one cw and the other ccw. lets ay you start with black red blueon motor # 1. bump the load with one motor to see if the shaft rortates in the proper direction. If it does and you are coming off a common feed then connect the 2nd unit red black blue.If the first motor is not roataing correctly just go red black blue on #1 and black red blue on #2.
[ August 04, 2004, 12:50 AM: Message edited by: stew ]
- Location
- Illinois
- Occupation
- retired electrician
Re: Standard Phase Rotation
While Charlie is correct that there are no requirements for conductor or bus bar phase identification, the code does specify a required "phase arrangement" for panels and MCCs. See 406.3(E) and 430.97(B).
Don
While Charlie is correct that there are no requirements for conductor or bus bar phase identification, the code does specify a required "phase arrangement" for panels and MCCs. See 406.3(E) and 430.97(B).
Don
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Standard Phase Rotation
Don,
You are correct in any one facility the phase location are specified as A-B-C-N front to back or left to right. Note, this relationship is not required at receptacles, nor at motor terminal boxes.
But, there is no such universal thing as PHASE A. After each serivce and SDS you get to refine which power leg is which phase. What the utility calls A has no bearing on what you call it. This specifically occurs in 240/120 3PH 4W systems where the utility wants the high leg to be C phase in the meter can, but the NEC says it needs to be B phase (in new construction).
Charlie,
There are many inexpensive phasing rotation meters available, there are even some that will work on de-energized motors.
Don,
You are correct in any one facility the phase location are specified as A-B-C-N front to back or left to right. Note, this relationship is not required at receptacles, nor at motor terminal boxes.
But, there is no such universal thing as PHASE A. After each serivce and SDS you get to refine which power leg is which phase. What the utility calls A has no bearing on what you call it. This specifically occurs in 240/120 3PH 4W systems where the utility wants the high leg to be C phase in the meter can, but the NEC says it needs to be B phase (in new construction).
Charlie,
There are many inexpensive phasing rotation meters available, there are even some that will work on de-energized motors.
Re: Standard Phase Rotation
Stew,
I have worked with some 3 ph automated valves that have built in circuitry to ensure that "open" is always "open" regardless of phase rotation. This is critical in some applications where jogging the motor could cause damage.
Also, our equipment arrives on site with the power distribution system pre-assembled. It is connected to the main feed by a sub-contractor then our guys complete the installation.
I was hoping that I could avoid haying the guys rework the motor wiring 50% of the time.
Don,
Do 408.3(E) and 430.97(B) imply that phase rotation should always be the same or are the feeds to the A bar and C bar be connected arbitrarily
Thanks,
Stew,
I have worked with some 3 ph automated valves that have built in circuitry to ensure that "open" is always "open" regardless of phase rotation. This is critical in some applications where jogging the motor could cause damage.
Also, our equipment arrives on site with the power distribution system pre-assembled. It is connected to the main feed by a sub-contractor then our guys complete the installation.
I was hoping that I could avoid haying the guys rework the motor wiring 50% of the time.
Don,
Do 408.3(E) and 430.97(B) imply that phase rotation should always be the same or are the feeds to the A bar and C bar be connected arbitrarily
Thanks,
- Location
- Illinois
- Occupation
- retired electrician
Re: Standard Phase Rotation
Jim,
Don
Jim,
Actually I think that there is, (not 100% sure) but it takes very very expensive equipment to identify it. Most of the the time we just look for correct rotation, ABC=BCA=CAB and the equipment doesn't care, but when systems or utilities are interconnected, A phase can only be connected to A phase. There are 3 major power interconnect grids in the US. Within the individual grids, you can only connect A phase to A phase. Rotation alone, is not enough for interconnection.
While some utility metering equipment requires that the high leg be landed in left or C phase position, it is still B phase as far as the rotation goes.
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: Standard Phase Rotation
mic,
Don
mic,
The wording implies that you must identify the actual phases and not just have "ABC" rotation.
Don
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Standard Phase Rotation
Don, you are correct about the basic interconnection of utility grids. However, the phasing on one side of a power transformer is not always the same as the other side (specifically in delta-wye configurations). This causes there to be no universally identifiable PHASE A. In reality, maybe this is only semantics but, the interconnection of power systems is dependent upon the synchronism of each phase not which one is first.
Don, you are correct about the basic interconnection of utility grids. However, the phasing on one side of a power transformer is not always the same as the other side (specifically in delta-wye configurations). This causes there to be no universally identifiable PHASE A. In reality, maybe this is only semantics but, the interconnection of power systems is dependent upon the synchronism of each phase not which one is first.
- Location
- Illinois
- Occupation
- retired electrician
Re: Standard Phase Rotation
Jim,
Don
Jim,
Yes there is a phase shift, but doesn't "A" still lead on both sides of the transfomer? I worked on a project where the utility almost made a closed transition tie in where they had one more delta/wye transformer on one of the two lines. The engineer I worked for was very insistant that the utility check between the two "A" phases. When they did, they found a voltage difference equal to the 30? delta/wye phase shift. We ended up starting the local generators, paralleling them with the old utility service, cutting loose from the old service, then paralleling the generators with the new service, and then shutting down the generators. This was all to avoid any outage time. It was a glass making plant and even a very short outage will result in reject glass for the next 18 to 36 hours.
If they are in sync, doesn't the same phase have to be first? If "A" is first on one line and "B" on the other, wouldn't we be out of sync by 120??
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: Standard Phase Rotation
Jim,
Don
Jim,
Yes there is a phase shift, but doesn't "A" still lead on both sides of the transfomer? I worked on a project where the utility almost made a closed transition tie in where they had one more delta/wye transformer on one of the two lines. The engineer I worked for was very insistant that the utility check between the two "A" phases. When they did, they found a voltage difference equal to the 30? delta/wye phase shift. We ended up starting the local generators, paralleling them with the old utility service, cutting loose from the old service, then paralleling the generators with the new service, and then shutting down the generators. This was all to avoid any outage time. It was a glass making plant and even a very short outage will result in reject glass for the next 18 to 36 hours.
If they are in sync, doesn't the same phase have to be first? If "A" is first on one line and "B" on the other, wouldn't we be out of sync by 120??
Don
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Standard Phase Rotation
Don, AC waveforms are always continuous with no beginning (other than at the immediate startup). There is no way (nor no need) to say that one wave form is occurring first, but you can say one does occur before a different one. But, once you pick a waveform as Phase A it can be used as a reference for all other phases.
Roughly speaking the term synchronized means the two wave forms have identical instantaneous values. Of course, these values need to include the frequency and voltage including whether it is rising or falling (polar coordinates work good here).
Don, AC waveforms are always continuous with no beginning (other than at the immediate startup). There is no way (nor no need) to say that one wave form is occurring first, but you can say one does occur before a different one. But, once you pick a waveform as Phase A it can be used as a reference for all other phases.
Roughly speaking the term synchronized means the two wave forms have identical instantaneous values. Of course, these values need to include the frequency and voltage including whether it is rising or falling (polar coordinates work good here).
charlie tuna
Senior Member
- Location
- Florida
Re: Standard Phase Rotation
it won't take long to field bump each motor individually to check rotation prior to operation. no instument- no guessing!
it won't take long to field bump each motor individually to check rotation prior to operation. no instument- no guessing!
- Location
- Illinois
- Occupation
- retired electrician
Re: Standard Phase Rotation
Charlie,
Don
Charlie,
That works fine in most cases, but some equipment cannot be run backwards and you must uncouple the motor from the equipment before you bump the motor. The labor cost required to uncouple and re-couple a number of motors will quickly pay for the test instruments.
Don
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Standard Phase Rotation
There are many refrigeration compressors that because of the oil pumps cannot be ran in reverse. And bumping them does nothing because there are no visible moving parts so rotation meter is the only way. I have one that has LED's that light up in the rotating direction to show a clock wise or counter clock wise rotation.
Hydraulic pumps are also in this category as most will be destroyed if ran backward.
There are many refrigeration compressors that because of the oil pumps cannot be ran in reverse. And bumping them does nothing because there are no visible moving parts so rotation meter is the only way. I have one that has LED's that light up in the rotating direction to show a clock wise or counter clock wise rotation.
Hydraulic pumps are also in this category as most will be destroyed if ran backward.
Re: Standard Phase Rotation
Mic, I'm sorry. I've seen these things in the real world and thought it would be rather easy to find one. Googe comes up with a dozen models but all are intended for the wrong side of the pond! I'm really suprised as e.g. Leviton has a wide range of pin and sleeve connectors. I don't know who would carry this type of item in the US. (I'm in Europe and never seem to learn to check US-Europe differences before opening my mouth :roll: )
Mic, I'm sorry. I've seen these things in the real world and thought it would be rather easy to find one. Googe comes up with a dozen models but all are intended for the wrong side of the pond! I'm really suprised as e.g. Leviton has a wide range of pin and sleeve connectors. I don't know who would carry this type of item in the US. (I'm in Europe and never seem to learn to check US-Europe differences before opening my mouth :roll: )
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