What is the techincal name for...
- Thread starter drews77
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chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
Not sure of the technical name, around here we would say, 'the motor is single phasing.'
jbelectric777
Senior Member
- Location
- NJ/PA
He may be referring to an "open delta" ? When a delta connected system loses a phase to a building or other structure the load can continue to be served but at only 60%
Cold Fusion
Senior Member
- Location
- way north
The technical term I use is, "lost one phase".
"3-phase system" is usually clear from the context.cf
- Location
- Logan, Utah
I have always referred that situation as "single phasing", but I don't know if that is the technical term for the situation.
Chris
mivey
Senior Member
It is as far as I know.
- Location
- Illinois
- Occupation
- retired electrician
When you lose one transformer of a 3 phase delta bank, you can continue to provide power at about 60%. When you lose a phase you can't supply power to 3 phase equipment.
"Phase loss" as in phase loss detection and protection in monitoring 3? fire suppression equipment.
Volta
Senior Member
- Location
- Columbus, Ohio
Drews, welcome to the forum. Technical or not, as others have said, 'single-phasing' is the common verb version, 'lost a phase' is the common descriptive complaint.
It might be that one 'phase leg', as I like to call the individual (usually) ungrounded conductors, has become disconnected after the transformers, or that an entire phase winding (between two {or more} legs) is no longer producing a voltage.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It sounds like the OP is asking about losing a line conductor. I believe our industry has managed to interchange the word Line (or Hot) with the word Phase, somewhere along the line forgetting that a 'phase' is a relationship not a single entity.
For the moment, ignoring any neutral conductor:
Two "line conductors" will provide (1) Line-Line voltage, which can easily be called 'single-phase'.
Three "line conductors" will provide (3) Line-Line voltages, which can be called 'three-phase'.
As I have stated many times, I see little, to no advantage, but lots of disadvantages for making the 'number of phases' dependent on the presence or absence of a neutral connection and the resultant L-N voltages.
For the moment, ignoring any neutral conductor:
Two "line conductors" will provide (1) Line-Line voltage, which can easily be called 'single-phase'.
Three "line conductors" will provide (3) Line-Line voltages, which can be called 'three-phase'.
As I have stated many times, I see little, to no advantage, but lots of disadvantages for making the 'number of phases' dependent on the presence or absence of a neutral connection and the resultant L-N voltages.
mivey
Senior Member
The single-phasing condition can occur on the secondary or primary side of the transformer. It makes a difference as to how the motor is connected and if the source transformer is wye/delta (or delta/wye).
With the loss of one phase on the secondary side, the motor can have two phases with 173% current and one phase with 0% current. Then, a delta-connected motor will experience normal current in two windings and 200% current in the winding opposite from the lost phase. A wye-connected motor will experience 173% current in two windings and 0% current in the winding with the lost phase.
With one phase lost on the primary side of a wye-delta source, the current to the motor can be 115% on two phases and 230% on the third phase.
It is common practice for the utility industry to call each primary conductor of a three-phase system with a multi-grounded neutral a phase. A line with 2 primary conductors and one neutral is referred to as 2-phase or "v"-phase. This recognizes that a load or winding can be connected line-neutral in addition to line-line. A line-neutral voltage can be a phase in the same manner that a line-line voltage can be a phase. Any voltage is defined by the relationship between two points (a designated point and its reference).
That being said, if you just have a delta system (no neutral) and lose one conductor, you are left with only two conductors (two points). Since a voltage is defined by the relationship between two points, this leaves you with one voltage and thus one phase (back-feeding, etc being ignored in this context).
Minuteman
Senior Member
- Location
- The Sooner Nation
Whenever we have a phase loss and/or a single phase condition, we refer to it as a a "lost leg".
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