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Author Information Topic:   Two phase ?
Member

   
Name: Len Bonosevich
Email: lennyelias@earthlink.net
Location: New hampshire
Title: Electrician
In Trade Since: 1976
Registered: Jan 2003
Total Posts: 186

 		posted January 09, 2003 at 01:46 PM       Edit/Delete Message
Would someone please explain terms: two phase four wire; and two phase five wire. Is two phase two ungrounded legs of three phase delta or wye? Thanks

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Member

   
Name: Andre Michalik
Email: amichalik@msn.com
Location: Illinois
Title: Electr. engineer, instructor, cert. inspector
In Trade Since: 1985
Registered: Jan 2002
Total Posts: 545

 		posted January 09, 2003 at 03:43 PM       Edit/Delete Message
Two phase is very rare configuration, used contemporary for stepping motors and servomotors. The phases are shifted 90 deg.
Four wire system has no galvanic connection between the phases. Five wire looks like "cross" with common center. As I know, the system is not generated nor distributed by any Power Company.
Andre

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Member

   
Name: Robert h Keis
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Location: Delaware
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 		posted January 09, 2003 at 04:29 PM       Edit/Delete Message
It is still used in parts of Philadelphia, PA.

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Member

   
Name: Steve Szymczak
Email: steve.szymczak@philips.com
Location: Illinois
Title: Electrician
In Trade Since: 1982
Registered: Oct 2002
Total Posts: 21

 		posted January 09, 2003 at 04:29 PM       Edit/Delete Message
For you trivia buffs, the original generators at Niagra Falls were two phase.

just my $.02

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Member

   
Name: Dereck Campbell
Email: dereck.campbell@mindspring.com
Location: Oklahoma
Title: Power quality enginer
In Trade Since: 1979
Registered: Aug 2002
Total Posts: 211

 		posted January 09, 2003 at 04:36 PM       Edit/Delete Message
Its used by the military. I believe it used to confuse the Russians.

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Member

   
Name: Al Hildenbrand
Email: al@alselectricworks.com
Location: Minnesota
Title: Electrical Contractor, BSEE
In Trade Since: 1968
Registered: Nov 2002
Total Posts: 28

 		posted January 09, 2003 at 05:38 PM       Edit/Delete Message
Len,

I like explaining 2Ø with an analogy to a 4 cylinder radial engine. You know? Radials like those used to turn the propeller of old airplanes.

To build the analogy: The voltage on the two hot legs of 120/240 single Ø "moves" like the pistons of a BMW motorcycle. The pistons are 180º apart (lying flat) and they share a common connection to the crankshaft (for the purpose of my example). When one piston moves in, the other moves out.

In your minds eye, add another set of cylinders, connected to the same place on the crankshaft as the first two, but instead of lying flat, imagine them up and down.

As the crankshaft turns, the pistons hit top dead center, first left, then top, right, bottom, left, etc. going around the circle. The voltage on the four hot wires of 2Ø swings positive the same way.

The fifth wire, 5 wire 2Ø, is a neutral. Whether it is there or not, depends on the transformer configuration.

Al

[This message has been edited by al@alselectricworks.com (edited January 09, 2003).]

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Member

   
Name: Mike Sorel
Email: mikesorel999@hotmail.com
Location: Canada
Title: Electrical enthusiast
In Trade Since: 2001
Registered: Dec 2002
Total Posts: 12

 		posted January 09, 2003 at 06:12 PM       Edit/Delete Message
Just to clear the air.

"Is two phase two ungrounded legs of three phase delta or wye?"

No
I think that would be considered a 1 phase branch. When the device is hooked up it would only see 1 sine wave, that of the amplitude diference between the two phase legs that the branch came from.

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Member

   
Name: Len Bonosevich
Email: lennyelias@earthlink.net
Location: New hampshire
Title: Electrician
In Trade Since: 1976
Registered: Jan 2003
Total Posts: 186

 		posted January 09, 2003 at 06:49 PM       Edit/Delete Message
Thanks all. I was fairly sure that two phase was used years ago in train yards and some metro areas. You have confirmed my original thought on the subject.

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Member

   
Name: Wayne Foster
Email: hurk27@attbi.com
Location: Indiana
Title: Electrician
In Trade Since: 1976
Registered: Jan 2002
Total Posts: 768

 		posted January 09, 2003 at 07:13 PM       Edit/Delete Message
It's also in use in some old draw bridges

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Member

   
Name: frank timmermeier
Email: frankselectrica@webtv.com
Location: Illinois
Title: Electrician/CONTRACTOR
In Trade Since: 1977
Registered: Jul 2001
Total Posts: 37

 		posted January 13, 2003 at 03:04 AM       Edit/Delete Message
DOES TWO PHASE HAVE TO BE GENERATED? WHAT DOES IT LOOK LIKE ON A SCOPE? WHAT WAS THE ADVANTAGE OF IT? WHAT VOLTAGES DID THEY USE? ON A FIVE WIRE CAN TOU USE SINGLE PHASE? WHAT HZ DID THEY USE? IS IT USED TODAY IF SO FOR WHAT REASON?

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