ECN Forum Forums Technical Discussion Electrical Theory and Applications 2 phase 4 wire schematic - last in the series

This final schematic demonstrates one of the methods of deriving 2 phase systems from a 3 phase source. Notice the 86% tapped coils and the 50% tapped coils.
This is known as the "Taylor Method". I know of one other 3 phase closed delta primary to 2 phase 4 wire connection - which uses 3 transformers. It's similar to this, just tap points are swapped around a bit.

Mostly the 2 phase setups were done by means of an open delta "Tee" connection for the primary, then the 2 phase 3/4 wire output was also connected in a "Tee" arrangement [AKA Scott - TEE connection. Funny, that name seems oddly familiar to me ].
An open delta Tee connection is done with tapped windings, whereas the more familiar open delta Vee connection is just a closed delta with 2 transformers instead of 3.

The outputs here are "Phase 1" [two wires] and "Phase 2" [also a set of two wires].
Between the conductors of a certain Phase, there is a potential [voltage], and each one is a stand-alone phasor [phase].
Phase offset between Phase 1 and Phase 2 is 90 degrees.

This is the infamous 2 phase system - which a simple 1 phase system gets mistakenly quoted as being

Comments??

Scott SET - the bringer of antiquated AC power systems

my edit is towards incorrect labels on phases - only noticed after posting -

[This message has been edited by Scott35 (edited 05-11-2001).]

whoo boy ! strange animal....is this what is described in 220-22 "5-wire, 2phase system", if so, where's the noodle?

Steve,

This one is just a straight 4 wire 2 phase type of Animal. I have a drawing [somewhere] that shows where the common neutral would be connected to, which would make this one a 5 wire system. I seem to remember it coming from a common connection to separate coils, so maybe it's a tap from the jumper which connects the outside coils' ends [??].

In Article 220-22, you can see there's a reference to both 2 phase 3 and 5 wire systems with a common neutral. A 5 wire system would be like the one shown in this schematic - just this one is lacking the before mentioned common neutral tap, but that system would be from a full 3 transformer bank.
The 3 wire system would be from two transformers connected in the "TEE" method. On that arrangement, one end from each coil are connected together to form a common connector [which would be the choice for grounding - if the system is to be grounded].
That guy would be the common neutral for the 3 wire 2 phase system.

I'll post the TEE connection schematics also, hust for fun. Now those are some odd looking Animals!!

Hope everyone likes this schematic! You will probably never see any of these 2 phase systems in your lifetime - unless accidentally stumbling across them in really old areas of Chicago, Ill. or Long Beach, CA.
I have only seen one, which was the result of pulling a serious "Mission" to find it.

Scott SET - bringing you large assortments of exotic Animals

it looks like one might possibly create this arrangement from a 3-ph x-former with really diverse taps????

not that i can understand why one would want such a system....

Scott E. Taylor?


It is clearly a four-phase system, compare to 6 and 9 phase systems to see why.

That's interesting that we sometimes don't count poles 180 degrees apart as separate phases.

would then a house, 240/120v be 2 phase?

What if B of phase 1 were grounded?

That's what I would have called it, to distinguish it, for example, from 220 V single pole.

Or A for that matter? (Assuming Scott doesn't mind explaining hypothetical reconfigurations to this rare design.)

Hi everyone,

So, does this one look odd, or what!!

It's an antiquated system, which is almost never used here in North America [only in real old areas where the customer still requires it].

It is derived from a 3 phase 3 wire closed delta primary [the primary on the line drawing is the side with referenced phases as "A", "B" and "C" - plus it is the delta triangle on the pictorial drawing].

The secondary coils need to have center taps and 86% taps [depending on the placement] - this creates voltages as required.

The secondaries are:
Phase 1 [consists of two wires, or "A" and "B" lines],
Phase 2 [consists of two wires, like Phase 1 does].
Each phase is a 1 phase 2 wire output.
The phase offset [degree of time lag] between Phase 1 and Phase 2 is 90 degrees.
Secondary values [KVA, EMFs and etc.] for polyphase loads [between Phase 1's "A" and Phase 2's "B", or vice verse] are 1.414 x the values of one stand alone phase.

Example:
If the output voltage per phase [between "A" and "B" on a certain phase] is 100 volts, then the phase to phase voltage [between A from Phase 1 and B from Phase 2] will be 141.4 volts.

Once again, if we look at only one phase of this system's output, there's only one individual phase [wave form].
There's only a phase displacement between the two separate phase outputs.

I would guess that if you want to make the system grounded, just pick one wire from only one phase [just one line, or coil end should be grounded - else the smoke gets let out ] and bond it to ground.

Phase to phase voltage will remain the same, but if for instance we ground "A" from Phase 1, then there's going to be 100 volts to ground from "B" on phase 1, 141.4 volts to ground from "B" on phase 2, and who knows what from "A" on phase 2 to ground [looks like it could be either zero, 112, or 86 volts]. I'll need to check this one in the good 'ol EE manual.

Now, as to this being a 4 phase system - when compared to a 6 or 9 phase system, I've heard this system misquoted as just that - a 4 phase 4 wire system. Once again, it did no harm, so no big deal for the inaccuracy.
If there was 2 sets of 4 wire outputs, then it would be a 4 phase transformer.

Not really sure what the 'Taylor" guy's first name is [wouldn't that be an absolute laugh if it was Scott E. Taylor - it would be kind of close..].

There is the "Scott - T" connection for 2 phase 3 and 4 wire - derived from open deltas connected in Tee, instead of Vee. Maybe the guy's name is Scott!!

I'm gonna have to log off now. Must get up early in the AM and go all over everywhere.
I'll try to respond to the other posts about the transformers in this forum tomorrow.

Scott SET - babbling a specialty

Scott,
is it possible to post the 'sine wave' for some of these?