How ph shift 120* works

[hbiss]

it seems this thread has lost him In complexity.

No need for it. All someone had to say was "they are born at 120 deg, not made from something else".

-Hal

 

[Carultch]

No need for it. All someone had to say was "they are born at 120 deg, not made from something else".

-Hal

And the reason they are born 120 degrees apart, is that the induction pickup coils of each phase in the generators, are spaced 120 degrees apart. Or a common fraction of 120 degrees, depending on the exact details of the generator geometry. In any case, it is the angle between the pickup coils along the generator rotation course, that sets the three phases to be 1/3 of a cycle apart in phase.

 

[Hv&Lv]

And the reason they are born 120 degrees apart, is that the induction pickup coils of each phase in the generators, are spaced 120 degrees apart. Or a common fraction of 120 degrees, depending on the exact details of the generator geometry. In any case, it is the angle between the pickup coils along the generator rotation course, that sets the three phases to be 1/3 of a cycle apart in phase.

Simplest and most concise explanation yet...
I posted the video to basically explain it that way..

 

[GoldDigger]

Regarding the argument that true uniform distribution over power phases cannot be done because there is no mechanism for phase shift of the real power load, that is not entirely true.
By using a wye on one side of a three phase transformer and delta on the other you can get phase shifts different from the basic 120 degrees. So by mixing two transformer configurations you might be able to get closer to a 180 degree phase shift. But you cannot actually get there.
Note that if am not asserting this as proven, since I do not feel up to doing the rigorous analysis. I am just proposing it as a possibility.

 

[Hv&Lv]

Regarding the argument that true uniform distribution over power phases cannot be done because there is no mechanism for phase shift of the real power load, that is not entirely true.
By using a wye on one side of a three phase transformer and delta on the other you can get phase shifts different from the basic 120 degrees. So by mixing two transformer configurations you might be able to get closer to a 180 degree phase shift. But you cannot actually get there.
Note that if am not asserting this as proven, since I do not feel up to doing the rigorous analysis. I am just proposing it as a possibility.

with different configurations you can shift 60 degrees for angles of 30, 90, 150.
and a Delta delta or wye wye can get you 180 degrees

 

[GoldDigger]

with different configurations you can shift 60 degrees for angles of 30, 90, 150.
and a Delta delta or wye wye can get you 180 degrees

So instead of combining 120 and 240 to get 180, you could combine 150 and 210 to get 180. But when you unwind it all back, does that do any better at distributing the load over the primary phases?
(My gut says it will not.)

 

[Hv&Lv]

So instead of combining 120 and 240 to get 180, you could combine 150 and 210 to get 180. But when you unwind it all back, does that do any better at distributing the load over the primary phases?
(My gut says it will not.)

It’s the way the primary and secondary are tied on each side that creates the shifts.
the wye wye and delta delta doesn’t have a shift when connected one way, but has a 180 shift when connected differently.
these three phases are shifted from primary to secondary side but the are still 120 separated from each individual phase.
this is completely off topic from the OP, as I’m talking about vector groups rather than 120 separation on a generator.
most common here is 30 degree lagging or 30 leading on a delta-wye power XF. They have to be the same when tying ends of circuits together or paralleling XFs.
easy enough to fix..

 

[Malywr]

It’s the way the primary and secondary are tied on each side that creates the shifts.
the wye wye and delta delta doesn’t have a shift when connected one way, but has a 180 shift when connected differently.
these three phases are shifted from primary to secondary side but the are still 120 separated from each individual phase.
this is completely off topic from the OP, as I’m talking about vector groups rather than 120 separation on a generator.
most common here is 30 degree lagging or 30 leading on a delta-wye power XF. They have to be the same when tying ends of circuits together or paralleling XFs.
easy enough to fix..

Thank you All for great response
Now I can understand that better.
Sometimes that puzzle me so I taught here is good place to ask.

 

[Strathead]

Thank you All for great response
Now I can understand that better.
Sometimes that puzzle me so I taught here is good place to ask.

I am glad you got some clarification. I understand basic electricity and I know (without truly understanding) many of the deeper things that have been touched on in this thread. If you are truly interested and you expect to stay with the electrical field, I suggest you learn AC and DC electrical theory, at least up through motors, capacitance, inductance, power factors etc. I hesitate to say how you should learn this as each of us learns differently, but I do suggest you do it in a structured way. Get a text book on theory and self teach, or take an online course, or actually enroll at you local community college.

 

[gar]

210608-2430 EDT

Assume sine wave excitation. If you consider a 2 phase motor, then one phase is shifted 90 deg from the other. The force vector moving the rotor is the product of the instantaneous voltage and current, or for convenience use either v or i squared. What is the hypotenuse of a right triangle? It is the square root of the sum of the two sides each squared. Thus, the rotational force vector is a constant independent of the angular position of the rotor. Therefore, instantaneous torque is a constant, like a good brushed commutator DC motor.

Same is true for a three phase motor. While a single phase motor has torque pulses.

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