Half right!
Half right!
Hello everyone btw. One day a co-worker and I were talking and he asked why do they call it single phase when there are two hot wires. I though about it for a minute and answered because it actually IS only one phase. It comes from your power supplier on only one line, It goes through a transformer the secondary coil is connected between the two outer taps, and the middle of the coil is center-tapped to get a mid point. Therefore it is single phase 240 with a grounded mid point.
When I asked my apprenticeship teacher he started drawing a picture of two sine waves 180? apart. And insisted it really was two distinct phases.
Who's right?
Don't know what else has been said here, but the voltages, V1 and V2, on L1 and L2, relative to the CT, are indeed 180 degrees apart as the sine waves indicate.
However, it is incorrect to imply that this is a 2-phase system because the extra "phase" is created by a simple inversion--not a second generator.
In other words:
The voltages, V1n and V2n, in a 120/240V 1-phase sytem are separated by 180 degrees.
The separation in the obsolete 2-phase system is 90 degrees, and a minimum of 3-wires and 2 transformers are required.