# Talk:Two-phase electric power

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material chopped out of three phase placed below it may be of use to expand on stuff here

Sometimes single phase center-tapped (split phase) 240 Vac is incorrectly referred to as "two-phase". It should be noted that a two phase system is a system in which the two voltages are 90° out of phase. For example, if one is $cos(2\pi\times 60t)$ and the other is $\sin(2\pi\times 60t)$, where t is time, then you have a two phase system, also known as a quadrature system (one being referred to as the real part and the other being referred to as the imaginary part). A two phase system for 120 Vac line to neutral will measure approximately 169.7 Vac line to line. Two phase systems are seldom used for high power because they require the same number of hookup wires as three-phase (i.e. one for sine, one for cosine, and a common wire) delta connection, and the two phase system also does not balance the same amount of electricity in each of the three wires (although the cosine and sine are balanced, the neutral is not the same as the other two). A two-phase system is said to provide complex power and such systems are used at lower voltages (e.g. for communications applications, or to run stepper motors, and the like) but not commonly distributed at high power levels.

I'll probablly look at integrating this stuff later if noone else does Plugwash 16:25, 21 Dec 2004 (UTC)

## Contents

### Has This Arrangement Ever Been Deployed?

It seems very natural, that in the power stations "grid transformer" the secondaries could be center tapped and earthed, thus producing two additional phases rotated 180° degrees from their source phase, making four phases 90° apart. In this way, at least the distribution network could operate with optimal copper, insulator plates and safety radius. If this has been used, I think it would bee worth to mention. — Preceding unsigned comment added by 88.195.7.227 (talk) 10:51, 10 November 2012 (UTC)

## I added a link

...for scott connection finally, and today a picture. Hope this helps.Cpswarrior 21:49, 21 April 2006 (UTC)

## Please

Please don't confuse the unwary reader with conflating "two phase" with "phase and return". Unless you can get a unique sense of rotation of a magnetic field out of it, it's not a polyphase system. It is useless and confusing to speak of "phases" when all you've got is a suppy wire and a return wire of instantaneously opposite polarity. The electrical business would be a lot clearer all around if people only spoke of "phases" in the context of a polyphase system, and encyclopedias ought to be models of clarity. --Wtshymanski 17:30, 25 August 2006 (UTC)

## Constant power?

"Furthermore, power transfer in a three-phase system with balanced loads is nearly constant, whereas it pulsates at twice the line frequency in single-phase systems and four times the line frequency in two-phase systems."

Cite or explain please? By my math, sine squared plus cosine squared is unity. Where does this supposed "pulsating" originate? 146.6.208.13 (talk) 21:22, 12 April 2011 (UTC)

Similar issue here: "These power pulsations tend to cause increased mechanical noise in transformer and motor laminations due to magnestriction and torsional vibration in generator and motor drive shafts."

Balanced 2- and 3-phase systems with linear loads deliver constant power. — Preceding unsigned comment added by 99.149.85.127 (talk) 14:04, 27 February 2014 (UTC)