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#14203 - 09/16/02 06:58 PM two phase?
Mike_Riverside Offline
Member

Registered: 08/18/02
Posts: 34
can someone please explain two phase power?
I understand single phase and three phase systems, but i dont see where two phase fits in.

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#14204 - 09/16/02 07:55 PM Re: two phase?
electric-ed Offline
Member

Registered: 07/08/02
Posts: 184
Loc: Canada
If you can think of single phase power as being similar to a single cylinder engine, with intermittent delivery of power to the load, and three phase power resembling a three cylinder engine, well, two phase power would be equivalent to, you guessed it, a two cylinder engine.

The two phase generator has two separate windings physically spaced so that the voltages are generated 90 degrees out of phase.

As a matter of interest, the generators at the first Niagara Falls power station, built in 1895, were two phase, 25 Hz, 2200 volts.

Ed

[This message has been edited by electric-ed (edited 09-16-2002).]

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#14205 - 09/16/02 08:26 PM Re: two phase?
Sean WB Offline
Member

Registered: 09/15/02
Posts: 113
Loc: South TX
You may generate 2 phase from any regular three phase system, if you use capacitors for changing the phase vectors acordingly. In fact, you may start with only 2 phases and neutral ( star connection ) out of the three phases. It's been along time since I calculated the phasors ( vectors ) for the capacitors. Maybe the easiest way is to do it graphically on milimetric paper. Another way to generate the 2 phases is wiring a small 3 phase transformer, delta-star insulated windings, in such a way that you obtain a phase angle right between the angle of two regular phases. Call that the zero degrees phase. Put two other windings in series, to make another phase, so that the new "phase" will be 90 degrees apart from the zero phase. Connect one wire from each phase to the other to obtain the common "neutral", and see if you can change Xformer taps or use a Variac to get both voltages equal, and preaferible equal to required motor voltage.

[This message has been edited by Sean WB (edited 09-16-2002).]
_________________________
I did not get as think so badly as you shocked I did.

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#14206 - 09/16/02 08:30 PM Re: two phase?
Sean WB Offline
Member

Registered: 09/15/02
Posts: 113
Loc: South TX
PS they have "phased" out 2 phase systems , you may run across this sometimes, I would avoid it if possible
_________________________
I did not get as think so badly as you shocked I did.

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#14207 - 09/16/02 08:42 PM Re: two phase?
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Wow, Sean, for a pre-Journeyman, you kick my Master butt...

_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#14208 - 09/16/02 08:44 PM Re: two phase?
ElectricAL Offline
Member

Registered: 10/10/01
Posts: 615
Loc: Minneapolis, MN USA
I like your image, Ed. Permit me to twist it just a little.

Think of the early aircraft engines with a single propeller. Right behind the propeller is the. . .what did they call'em, radial cylinders of all the pistons that power the prop. The crankshaft that the prop is mounted to has only one saddle in it, and all the connecting rods of all the pistons connect to that one spot.

Single phase 120 V would have one piston.

Single phase 3 wire 120/240 V would have two pistons opposite each other, 180 degrees apart.

Three phase, either 120/208 V four wire or 240 V three wire would have three pistons equally spaced from each other, 120 degrees apart.

Two phase would have four pistons, at right angles to each other, 90 degrees apart.

Al
_________________________
Al Hildenbrand

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#14209 - 09/16/02 08:49 PM Re: two phase?
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Sweet motor!

What's the HP? The weight? RPM?

I didn't know Rotec was making modern radials!

Gorgeous!

Harley Davidson Evo x 3.5!

*drooling*
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#14210 - 09/16/02 08:49 PM Re: two phase?
Sean WB Offline
Member

Registered: 09/15/02
Posts: 113
Loc: South TX
its not imprtant to know everything, it is important to know where to get the information!!!
Hey ,consider me a journeyman, this saturday at 12 noon!!!!
sparky66 are you the one who took the master 2 months after getting journeyman?? How the heck did you do that??
confident from passing journeyman?? was it the SBCCI?
_________________________
I did not get as think so badly as you shocked I did.

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#14211 - 09/16/02 08:52 PM Re: two phase?
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Nope, not me... I had a good 12 months between, maybe a little more...

Did I typo in a thread somewhere?

WV requires one year, and I did come close to that minimum.

Go get 'em on Saturday, Sean!
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#14212 - 09/16/02 11:30 PM Re: two phase?
txsparky Offline
Member

Registered: 05/25/01
Posts: 578
Loc: Magnolia,.Texas U.S.A.
Sean,that was me.Yes it was SBCCI.There is not alot of difference in the two tests (on the open book part) and it just seemed easier to continue prepping for the Masters exam.I already had Houston and Conroe journeyman card

I'm with Sparky66wv,sounds like you won't have any problem passing Saturday

GOOD LUCK!!!

[This message has been edited by txsparky (edited 09-17-2002).]

[This message has been edited by txsparky (edited 09-17-2002).]
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