"Single-phase" 240VAC in North America is comprised of TWO phases of 120VAC which are 180 degrees out of phase with each other. In a 4-wire hookup, there are two phases of 120VAC, a neutral, and a ground. When you measure between the two phases of 120VAC, you get 240VAC.
In countries where the regular line voltage is 240VAC (such as Europe), there is a 3-wire connection with 240VAC, Neutral, and Ground. 240VAC to Neutral is really 240VAC.
Needless to say, the North American version is ambiguous and confusing. It would be more accurate to call it dual-phase 120VAC, or something like that. Again I ask, Why?
2007-02-12 07:08:19 · 6 answers · asked by knowmeansknow 4 in Science & Mathematics ➔ Engineering
No, it is called split-phase when you access it from a center tap.
http://www.allaboutcircuits.com/vol_2/chpt_10/1.html
2007-02-18 05:06:36 · answer #1 · answered by Mike1942f 7 · 0⤊ 0⤋
Good question.....I think it because the two phases are additive and a scope pattern of the 240 VAC (120 VAC - 120 VAC) line will clearly show a double phase of 120 AC. At 90 and 270 degrees, it will be 120 V negative and 120 V positive for a potential of 240 V - at no time (other than zero) will the positive or negative going wave be the same potential. When either line is connected to neutral, again, it will only show a single phase, this time 120 VAC.
This is to differentiate it from true multi-phase power sources which will clearly show multiple phases at the same polarity on a scope and is not additive.
2007-02-12 07:31:27 · answer #2 · answered by LeAnne 7 · 0⤊ 0⤋
In the US we have 240 VAC Single phase which-as you discussed above is made by two phases of 110. This hook-up is used in residencial units primarily for electric stoves and dryers.
We also have 240 volt 3 phase -used in industry for electric motors and industiral equipment. Same as 480 3 phase-just half the voltage
2007-02-12 07:35:56 · answer #3 · answered by Allen L 3 · 0⤊ 0⤋
Our normal is a Y transformer and that will give 240 v between phases and 120 from either phase to neutral. Be careful they can shift taps and get almost anything.
2007-02-12 08:19:46 · answer #4 · answered by JOHNNIE B 7 · 0⤊ 0⤋
The sine wave of the current is the phase. What would you do, break up the wave into two parts? Why not three or four?
Look up the definition of phase and you will see that it refers to the complete cycle.
2007-02-20 02:52:21 · answer #5 · answered by H.C.Will 3 · 0⤊ 0⤋
Here's a read...have fun:
http://en.wikipedia.org/wiki/Single-phase_electric_power
2007-02-12 07:18:31 · answer #6 · answered by tmlamora1 4 · 0⤊ 0⤋