Holy Cow!!! What a thread!
Holy Cow!!! What a thread!
Man, this thread is going everywhere - and not stopping to take a break either!
It has covered the simple stuff in major detail, but inaccuracies are thrown in here and there.
Time For A Monkey Wrench To Be Tossed in!!!
(this may have been mentioned already, so if it has, I'm sorry for the redundancy!)
Example Secondary Configuration:
3? 4W Wye (3 Phase 4 Wire Wye) - 208Y/120V
3 Ungrounded Conductors - derived from Secondary Terminal Bushings "X1" of each 1 Phase 2 Wire Winding (terminals viewed as "X2" on left, "X1" on right).
Call these Lines "A", "B" and "C".
Common Grounded Conductor derived from tapping into the "Series Jumper" which bonds all 3 of the remaining "X2" terminal bushings together.
Call this "N"
[i[just setting things up for pseudo suspence![/i]
Am I completely out of my mind, if I was to refer to the following loads connections to be supplied by a Polyphase Circuit?:
Load = 12 Ohm Resistor, between Line "A" and "N",
Load = 12 Ohm Resistor, between Line "B" and "N",
Load = 20.8 Ohm Resistor, between Line "A" and Line "B"
Do I have a 3 Phase 3 Wire Circuit here???
Would this be considered an "Open Wye"?
Think this one through a bit before replying!
Personal thoughts:
2 Wire Circuits derived from Polyphase systems are simply 1 Phase 2 Wire Circuits.
No "180 degree Phase Displacement" taking place - regardless of what extraordinary tweeked methods are used to achieve a workable result
(isn't it strange how hard it is to make it work, with the 180 degree offset concept - as opposed to how it simply works out seeing no offset?).
If the 2 Wire Circuit was Line A and Line C from a 4 Wire Wye, there is still only a single phase situation going on. Only one Current is flowing through the load, driven from two windings in series.
Nothing is available to reference any type of offset, since there are only two wires involved.
Additionally, each Line to Common (Neutral) 2 wire circuit from the 4 Wire Wye is simply a 1 phase 2 wire circuit, with no offset.
Add that Common Grounded Conductor with 2 or all 3 Lines, and now there is a Polyphase arrangement.
In fact, 2 Ungrounded Conductors + the Common Grounded Conductor could drive the Primary of a 3 Phase Transformer, and result in a 3 Phase output on the Secondary.
This Transformer's Primary would need to be setup for 2 different input Voltages, but it would have a single voltage Secondary (unless connections are made to achieve dual voltages).
For a Delta 4 Wire setup, the Transformer with the Center Tap will be the same as a stand alone 1 phase 3 wire setup from a single Transformer.
This is true of both Open and Closed 4 Wire Deltas.
If the "High Leg" was introduced into a Multiwire Circuit (with the Center Tapped Neutral), the Currents may flow at different times, but these will still be 1 phase arrangements.
The normal setup for 3 wire circuitry would be a result of 2 Ungrounded Conductors derived from the outer terminal bushings of the center tapped secondary winding, and the system's grounded conductor being derived from the center tap of that Transformer's Winding.
Again, no "Phase Difference" will take place, because the currents all originate on a Single Winding.
As to a "Stand Alone" 1 Phase 3 Wire system, this may be derived from either a single Winding with a physical tap made to the mid point of the Secondary Winding, or it may be from the Series Adding configuration of 2 individual split coil Secondary Windings - with a tap made to the "Series Jumper" between the 2 windings.
If there was an offset of 180 degrees on the Secondary Winding, there would be no Voltage created - since the waves would cancel each other out.
No Voltage created, no Current can be "pushed" through loads - and the system is of no value.
The magnetic flow in the core cuts across the _ENTIRE WINDING_ in one direction, then reverses direction - resulting in a single phase Voltage and Current being created on the Secondary Winding.
It runs across the winding in the same direction each part of the cycle, so that in it's self would indicate no "phase offset".
The way a Center Tapped 240 Volt Winding creates a Voltage of 120 Volts at the Center Tap is because it is at a point where only 50% of the _TOTAL WINDING'S POTENTIAL_ is achieved - regardless if the reference is between the Left side of the coil and the center tap, or if the reference is between the Right side of the coil and the center tap.
Same goes for a multi tapped Secondary - typical of Audio Amplifiers (especially Tube Amps!!!).
No "phase offset" between any 2 taps, or the ends of the Winding.
I could have a Single Phase Winding with 7 taps across various points of the winding. Each tap point would have a Voltage between other tap points, or the ends of the coil, so therefore, loads could be connected to anything on this coil and a _SINGLE PHASE_ Current would flow in the loads.
As to a 2 Phase system, these Animals may be thought of as having "Two Individual Sets Of 1 Phase 2 Wire Terminations"
It's easier to invision this with a typical 2 Phase 4 Wire system - there are 2 "Sets" of "Phases" - "Phase 1" is a 2 Wire Single Phase circuit, and "Phase 2" is another 2 Wire Single Phase circuit.
2 Phase 5 Wire circuitry is done to create a 1 phase 3 Wire Multiwire circuit, for Lighting and Receptacle use. The "5th Wire" is a tap done to obtain a "Neutral Conductor" from one set of windings. This 5th Wire also becomes the System's Grounded Conductor - although, in theory (not per any code), any single system Conductor may be bonded to Earth + Metallic Equipment, and form the System's Grounded Conductor.
This is true of _ANY_ Grounded AC Power System.
Let the Fireworks begin!!!
Scott
p.s. there are a zillion Transformer Drawings at ECN's Technical Reference section - along with Motors.
You may find quite a few 1 Phase setups, along with 2 phase systems, 3 phase systems, 6 and 9 phase systems, plus 1 phase, 2 phase, 3 phase and 6 phase Motors.
Sorry for the "Mini Series Post", believe it or not, this is short, compared to what I was going to post
