Is it Single or Two Phase?

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rattus said:
I would argue that "phase shift" is commonly used to indicate current lead or lag which is limited to +/- pi/2 in practice.
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Sure... when limiting an evaluation to a single voltage source and bringing reactance into the equation.

rattus said:
If we are describing 3-ph voltage or current relative to zero, phi can be any value in the cycle but must be less than 2pi.
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Bringing current and reactance into the 3? discussion actually expands the effective range by + and ? 90?. However, as convention usually dictates, suffice it to say all voltages and currents can be assigned angle values that put them within the one cycle period of the reference voltage.
 
For Jim Dungar:

For Jim Dungar:

Consider the attached circuit diagram. Schematically, it is identical to the 1-ph circuit we have used earlier. This time however, I choose to let it represent two legs of a wye service. The third leg is open.

Now let,

V1n = 120V /0
V2n = 120V /-120

Then,

V12 = 120V /0 - 120Vrms/-120
= 208V /30

The senses of I1 and I2 are chosen to agree with convention. In so doing, we force In to be the sum of I1 and I2.

I1 = 120V /0/10ohms = 12A /0
I2 = 120V /-120/8ohms = 15A /-120
I12 = 208V /30/12ohms = 17.3A/30

Iv1 = 12A /0 + 17.3A /30
Iv2 = 15A /-120 - [17.3A /30]
In = 12A /0 + 15A /-120

I won?t bore you with the trig, but I will make the point that this problem is a bit more complex than is the 1-ph problem, and I see no advantage in taking the negative of one of the voltages. You cannot do this one in your head.

Rattus
 
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