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- Wisconsin
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- PE (Retired) - Power Systems
I count phases by the number of L-L voltages, so I have no problem with this terminology.
Dual Phase
- Thread starter Besoeker3
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kwired
Electron manager
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- NE Nebraska
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Good way to look at it as a general rule.
The open wye/open delta transformer arrangement kind of complicates this a little though.
as does true two phase you'll get three voltages.
kwired
Electron manager
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Two phase 5 wire in a + configuration has 6 line to line voltages doesn't it?
Oh yeah your right 240V X 2 and 170V X 4
winnie
Senior Member
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- Springfield, MA, USA
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- Electric motor research
For a while now I've been working with 'high phase order' motors.
We got some interesting results specifically playing with the different L-L voltages available. 8 different voltages available in a 17 phase system, with 17 different phase angles at each voltage
Jon
We got some interesting results specifically playing with the different L-L voltages available. 8 different voltages available in a 17 phase system, with 17 different phase angles at each voltage
Jon
- Location
- Wisconsin
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- PE (Retired) - Power Systems
Not if you follow my method of ignoring the common/neutral wire and transformer taps, so effectively only the highest L-L voltages are counted.
Frank DuVal
Senior Member
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- Electrical Contractor, Electrical Engineer
Sure is single phase. Two phases would show as two sine waves on an oscilloscope. When you hook the leads to the 240 connection, you see one sine wave. Keeping one lead in place, move the other lead to the neutral. Still see one sine wave. Therefore single phase.
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No matter what two wires you connect to you will see only a single phase on a single trace scope.
If you trigger off L1-N for a consistent time reference you will see the same or 180 different phase for all other connections on a 120-0-120 split phase.
If you do the same on a 2 out of 3, which was Jim's subject in post #7, you will see a 120 degree phase difference.
If you have a dual trace scope and trigger consistently off one channel, dual phase will show a 0 or 180 degree shift
With the same dual trace scope and trigger setup a 2 out of 3 source will show a 120 degree offset.
If I understand your counting stratagy and Philly 5 wire two phase you have:
- 240V between a - aa
- 240V between b-bb
- 170V a-b
- 170V a-bb
- 170V aa-b
- 170V aa-bb
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- Wisconsin
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- PE (Retired) - Power Systems
And only two of those voltages are 'high' so that is all I would count. The other four voltages would be used to determine the actual system configuration beyond the simple number of phases.
ggunn
PE (Electrical), NABCEP certified
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- Austin, TX, USA
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- Consulting Electrical Engineer - Photovoltaic Systems
Wow. If we would have gone to four phases instead of three we could have gotten around the whole stupid square root of three thing.
winnie
Senior Member
- Location
- Springfield, MA, USA
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- Electric motor research
Wow. If we would have gone to four phases instead of three we could have gotten around the whole stupid square root of three thing.
And if we when with 5 phases we would get 2*sin(72°) as our stupid conversion number
-Jon
wwhitney
Senior Member
- Location
- Berkeley, CA
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That rule works nicely for most cases, but it would call 2-phase 3-wire "single phase", as there is only one L-L voltage, and that is higher than either L-N voltage.
Cheers, Wayne
- Location
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- PE (Retired) - Power Systems
Yeah.
But I use it as a working rule of thumb, not as an absolute for esoteric systems.
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