The term "polyphase"

[mivey]

"In a multiphase system the individual phases are SOMEHOW galvanically related to each other, as one phase is referenced to another or grounded commons. etc." Consequently; when you galvanically isolate the individual phases from each other they seize to be a multiphase system.

I agree that their must be some common reference frame but I'm not so sure that the exchange of charge carriers is required for a system to be called a polyphase system. The windings could be separate.

 

[mivey]

They don't need to be of equal magnitude to have a phase difference.

Of course not, but I was discussing grouping voltages with equal magnitudes. That is part of what makes up what we call a polyphase system.

I suppose you could have some windings designed to run at one voltage and some at another but who does that? Still, a mixture of different magnitudes is not what makes a classic n-phase system.

 

[beanland]

Oh, Oh, I just have to add: Polygon Transformer

Oh, Oh, I just have to add: Polygon Transformer

A polygon transformer can turn 3-phase polyphase into any number of poly-phases, each with a different phase angle relative to some reference. Poly = many so don't limit polyphase to 2-phase at 90 degrees, 3-phase at 120 degrees or even 6-phase at 60 degrees.

 

[Besoeker]

I suppose you could have some windings designed to run at one voltage and some at another but who does that?

For phase-controlled systems for rectifiers, DC drives, burst firing heater systems, you need synchronising waveforms referenced to the power circuit.
Different voltages apply.

 

[mivey]

For phase-controlled systems for rectifiers, DC drives, burst firing heater systems, you need synchronising waveforms referenced to the power circuit.
Different voltages apply.

So you would call three voltages consisting of 120v @ 0deg, 208v @150 deg, and 480v @270 deg a polyphase system and refer to it as a 3-phase system?

 

[Besoeker]

So you would call three voltages consisting of 120v @ 0deg, 208v @150 deg, and 480v @270 deg a polyphase system and refer to it as a 3-phase system?

Call it what you want.
I was simply making the point that hey don't need to be of equal magnitude to have a phase difference.

 

[mivey]

Call it what you want.
I was simply making the point that hey don't need to be of equal magnitude to have a phase difference.

ok. I agree with the obvious. I thought you were going somewhere with that.

 

[Besoeker]

ok. I agree with the obvious. I thought you were going somewhere with that.

I got where I was going with it.
You commented "A unique phase in a set of voltages with equal magnitudes and frequencies"
That bit about equal magnitudes is wrong - or at least not part of the necessary requirements.

 

[mivey]

I got where I was going with it.

I was holding out for an alternative definition of polyphase circuits. Certainly you weren't just making a statement about voltages in general as that would be stating something that is obvious to almost everyone and is not really useful given the context. Perhaps your "call it what you want" comment suggests you were doing just that, but I was thinking you wouldn't.

You commented "A unique phase in a set of voltages with equal magnitudes and frequencies"
That bit about equal magnitudes is wrong

Can't be so. I was discussing a polyphase system and it is my choice as to what I want to include.

If I choose to segregate red 4-door cars, that is not the same as saying all 4-door cars are red. I chose to segregate voltages in the same way that is classically done when defining polyphase systems.

- or at least not part of the necessary requirements.

It is given the normal definition for polyphase systems.

There are many references but here is one from the Fitzgerald classic "Electric Machinery"

Generation, transmission, and heavy-power utilization of ac electric energy almost invariably involve a type of system or circuit called a polyphase system or polyphase circuit. In such a system, each voltage source consists of a group of voltages having related magnitudes and phase angles. Thus, an n-phase system employs voltage sources which typically consist of n voltages substantially equal in magnitude and successively displaced by a phase angle of 360?/n.

If you have an alternative definition for polyphase systems, let's hear it.

 

[jumper]

Mivey, good to see you my friend!!!

 

[mivey]

Mivey, good to see you my friend!!!

Why thank you sir. Better to be seen than viewed.

 

[Besoeker]

I was holding out for an alternative definition of polyphase circuits. Certainly you weren't just making a statement about voltages in general as that would be stating something that is obvious to almost everyone and is not really useful given the context. Perhaps your "call it what you want" comment suggests you were doing just that, but I was thinking you wouldn't.
Can't be so. I was discussing a polyphase system and it is my choice as to what I want to include.

I was simply pointing out that you can have a number of phases(poly) that are related in terms of phases but of different magnitude. We have a printed circuit for controlling the conduction angles of SCR circuits. The phase relationship between the synchronising voltages and supply voltages is well defined. The magnitudes are totally different

There are many references but here is one from the Fitzgerald classic "Electric Machinery"

Generation, transmission, and heavy-power utilization of ac electric energy almost invariably involve a type of system or circuit called a polyphase system or polyphase circuit. In such a system, each voltage source consists of a group of voltages having related magnitudes and phase angles. Thus, an n-phase system employs voltage sources which typically consist of n voltages substantially equal in magnitude and successively displaced by a phase angle of 360?/n.

I'd say it is a pretty good definition for most typical generation, transmission, and heavy-power utilization of ac electric energy.