Do 2 coils 90? apart supply a 2phase load ?

[al hildenbrand]

And that couldn't have been done with 90? 2phase ?

David,

The mathematical principals in Fortesque's Symetrical Components can be applied to any polyphase system of n phases where n is greater than 1, so, yes, one can analyze a two phase system with symetrical components.

The limited amount of long distance two phase transmission line is what says to me that there wasn't a lot of valuable transmission line and/or two phase generators that would get the development dollars to design, manufacture and install protective relays by the 1920s and 30s when the first applications of the math were occuring.

Before symetrical component math, a four wire, two phase generator without a common "neutral", would behave in understandable ways if the centertap of the windings were not connected together. The lack of the bond left the generator, essentially, as two separate single phase generators offset by 90? of rotation. The unbalanced or assymetrical conditions imposed on the two single phase parts of the generator could be understood by the mathematics of the late 1800s, and protection schemes for faults worked.

 

[dnem]

Thanks everybody !
It was a good thread !

David

 

[LarryFine]

One last question.

I can see the 120? difference in the sine wave pattern with the ground a flat base line reference line for a wye system.
I can see 120? difference in the angles of the wye.
I can see the 120? difference in the sine wave pattern with the ground a flat base line reference line for a delta system.
So why an I looking at a 60? difference in the angles of the delta ?

Here's one I can answer.

Imagine the graphic drawing of three vectors leaving 0,0 at the usual 120 degrees apart, like a Mercedes star, with arrows on the tips. Or, if you prefer, the typical 208/120v 3-phase layout, with neutral in the middle.

Now, imagine that you can pick up the three arrows, and rearrange them so they form a triangle, with the point of each arrow at the tail end of the next one. Now there are three 60-degree angles inside the triangle.

Notice how much this resembles a Delta? That's because it is. (120 degrees and 60 degrees are complimentary angles, which always add to 180.) This is what Winnie meant when he said " Simply point of view."