2-phase AC motors? 1

[RDombek]

I'm not sure if anyone is familiar with this, but Dewalt has teamed up with PAL publications and has an Electric Motor professional reference (similar to Ugly's). This one I'm refering to is specific to motors.

Anyway, I see on a few pages references to 3-wire and 4-wire, 2-phase AC motors. Has anyone heard of 2-phase motors and what if any applications would use these? If anyone has the book it shows the connections on page 3-6 and also refers to 2 and 3 phase applications on pages 4-6 and 4-7.

 

[aolalde]

Several years ago it was regular to find 1 phase, 2 phase or three phase electric systems and motors.
Actually we have adopted as more common, 3-phase and Single phase. Although Systems with more than 3-phases are feasible depending on the application requirements, certainly those are not common.

 

[davidbeach]

2 phase is a historic anachronism. There may well still be some systems, I doubt there have been any new installations for a very long time. The two phases in a 2 phase system are in quadrature; in a 3 wire system, the two phases share a common conductor while in a 4 wire system each of the two phases have two conductors independent of the other phase.

 

[jtkirb]

I just serviced a hydro plant (excitation problem) that is 2 phase hooked to a scott-t transformer connection to get 3 phase out of the plant. Old as hell, but still runs without issue. The last 2 phase generator I am aware of in Michigan.

The books keep this info around because once in a great while you come across the need for the information. Chances are you will never see one in operation...unless you want a tour.
JTK

 

[stevenal]

Application? Where ever you need a self starting motor where two phase service is available. Con Ed must have it somewhere, see page 5:

http://www.coned.com/documents/elec/018-024.pdf

 

[sreid]

At least as amazing, direct current service is provided for existing locations.

 

[nbucska]

In some magnetic hard disk drives 2-phase motors were used
to simplify the elelctronics.


<nbucska@pc33peripherals.com> omit 33 Use subj: ENG-TIPS
Plesae read FAQ240-1032

 

[waross]

Thank you stevenal for a fascinating link.

Years ago, B.C. Electric, and later it’s successor B.C. Hydro and Power supplied DC from the electric streetcar lines and later the trolley bus lines. It was used for elevator service in the downtown core. The last I heard about it was 30 or more years ago. A Hydro engineer mentioned that they were starting to put in rectifier supplys from the AC service rather than tapping the trolley lines. They may be still supplying DC. Does anybody from western Canada know?
I thought 2 Phase went out before 25 Hz. And as far as I know 25 Hz. has been gone for 50 years or so. Is there any 25 Hz left anywhere?
yours

 

[DickDV]

I believe that there are still a couple of buildings inside the USSteel Gary Works that are 25Hz.

 

[waross]

Hello DickDV
Years ago I read an interesting paper on a 25Hz installation that was done with old equipment from the warehouse. When the mill was making the last changeover to 60 Hz there was one piece of equipment (possible an induction furnace) that was not suitable for conversion to 60Hz. There where a lot of surplus 25 Hz synchronous machines, but nothing big enough to run the furnace. They set up two MG sets, each consisted of a 60 Hz machine driving a 25 Hz machine.
The trick was to parallel them. The synchronous motors locked on to the freqency. The speed could not be changed to bring them into synchronization. They built a micrometer adjustable coupling for one of the sets. They would run both sets and measure the phase difference between them. Then stop the sets and adjust the coupling to advance or retard one machine slightly. When they got it, no further adjustment was required. They could just start both machines and close the tie breaker.
yours

 

[jtkirb]

That sync method is different and sort of cool. I once was setting the speed of a slow turning horiz shaft hydro with a flourecent light fixture- worked just like a timing light.

JTK

 

[waross]

You do what you gotta do.
I once localized a ground in a 13KV cable with a wheatstone bridge made out of a multimeter, a tape measure, a guitar string and a truck battery and with everything except the battery up on the pole at the pothead.

 

[tinfoil]

Rankin generating station at Niagara Falls STILL generates at 25Hz, and there us still some 25Hz load on the US side.

 

[waross]

Thanks tinfoil
Fasinating.
yours

 

[RDombek]

Thank you all for the info.! It's interesting to hear what's still out there from the 'electrical troops'.

 

[ebarl]

I'm glad to hear 2-phase is still talked about. I was wondering if anyone knows of a way to run a two-phase, four wire motor from a three-phase service?

General Electric has said the motor I have is about 65 years old. The the motor is attached to a machine aquired from a shop in Philidelphia. The people claim it has run recently but I'm not aware two-phase service is still available in that part of the country.

 

[davidbeach]

google for Scott transformer, hopefully you will find something.