ECN Forum Forums General Topics of the Trade General Discussion Area two phase?

'66

I believe that's the Rotec 2800: Total swept volume of 2800cc (172ci). 110HP @ 3700 RPM geared. Total engine diameter is 810mm (31.9"). Dry Weight is 108kg (220 lbs) complete with bolt on engine accessories.

Al

Modern stepper motors that are used for robotics and motion control applications operate from an electonically produced version of two phase power.

Ed

For giggles see 99NEC Table 430-149. {Is it in the 2002 edition?}

Footnote: Sometimes the term “two phase” is incorrectly used to describe 1) 120/240V 3-wire service {which is still single phase} or, 2) two ungrounded conductors and a neutral are tapped from a 4-wire wye system {which is correctly termed ‘network service.’}

Two-phase may be mentioned in the fine print of some electric utility’s service agreements, but it is always qualified as “not for new work,” and sometimes with verbiage to the effect of, “If we own special equipment to provide you, the customer, with two-phase service, and it breaks, you have to, at that time, now accept three-phase service from us,” effectively mandating an upgrade of your old stuff at your expense.

I understand that the Sierra Nevada mountains in the early past century had sawmills with 2-phase motors. Also, two-phase power was described as once popular in the "Philadelphia District."

Yep,

2002 NEC Table 430.149 Full-Load Current, Two-Phase Alternating-Current Motors (4-Wire).

Gentlemen:
For what it's worth, I faintly remember going to the Philadelphia area, a long time ago, with one of the "old timers".
I think it was some type of hotel, and it had two phase power. Can't remember all of the details; something about "2 hots, 2 neutrals, & 1 grd" maybe?????
Had to be in mid 70's???

John

Thanks for the repies. I was not planning on doing any work with it...I was just curious...I was reading somthing about philadelphia and saw two-phase mentioned.

I have also heard of other poly-phase systems...such as six-phase??? maybe this is used for large equipment? I have never heard of this being used.

Mike,
With regard to you last comments about Six-Phase wiring, I come from New Zealand and we quite regularly hook up motors, in a configuration we call 'Star-Delta', this uses a 3-phase motor (400V), the motor starts in Star, and runs in Delta, this requires that there are two 3-phase wires
running to the motor, hence the 6 phases.
Just as a note, polyphase in my language,
means any circuit that has more than one
un-earthed(live)conductor.
Normally poly-phase over here means 3-phase
400V, wether or not that it has a Neutral conductor.

The star-delta motor configuration is also commonly used on larger motor starters in England.

The only problem with that definition is that is falls down when we come to a single-phase 3-wire service, such as the normal 120/240V American residential system.