May be a dumb question but, knowing that a lot of philadelphia was ran on two-phase, is/was it common to "replace" that with two single-phase mains coming in? I was asked about an ancient elevator not working while the guy is waiting on the elevator guys.. I assume that the elevator was two phase and since it is now hooked up to two single phase, that is most likely why it's not working? Any ideas? The only thing that would run on anything other than single-phase would be the elevator.. any insight/philadelphia electrical system history would be greatly appreciated, haha.
Philly power...
- Thread starter DSantilli
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
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- Electrical Contractor
D, welcome to the forum! 
Rule #1: We don't allow dumb questions. Fortunately, there aren't any, so you're okay.
No, 2-phase power is made up of two sources separated by 90 degrees. You can't get that by simply applying either single phase or two lines of 3-phase power.
2-phase power can be derived from a 3-phase supply by using what's known as a Scott-T transformer. Google it. You'll find more about it than we could explain here.
In the meanwhile, don't risk burning out the existing motor by experimenting. The alternative is to 'modernize' and replace the motor and its controls with 3-phase.
Rule #1: We don't allow dumb questions. Fortunately, there aren't any, so you're okay.
No, 2-phase power is made up of two sources separated by 90 degrees. You can't get that by simply applying either single phase or two lines of 3-phase power.
2-phase power can be derived from a 3-phase supply by using what's known as a Scott-T transformer. Google it. You'll find more about it than we could explain here.
In the meanwhile, don't risk burning out the existing motor by experimenting. The alternative is to 'modernize' and replace the motor and its controls with 3-phase.
I would think that a 2-ph motor would run--light load--on the two phases from an open wye, but the separation would be 120 degrees instead of 90. But, I doubt that you could obtain rated horsepower, and you would likely get some smoke as well. I wouldn't do it except as in a controlled lab experiment.
conmgt
Senior Member
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- 2 Phase Philly
I own a commercial building in Philly with 2 phase and a 2 phase elevator. When I finish the new 3 phase service, I'll run the elevator on a phase converter.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Is that more economical and/or relaible than a Scott-T transformer?
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