Re: Can someone explain the difference between phases and poles??
Primary side Secondary side.
The poles are the three legs of the secondary side of the trans former. The top leg is line 1 (hot) the bottom is line 2 (hot) the center is the common. All legs have voltage and current flow but the center is tied to ground, that references it to ground so you see no voltage difference between it and ground. As the current is flowing out of the top leg it is flowing in the bottom leg so the current flow is in opposite directions on the two legs then reverses direction.This happens 60 times per second. Measuring between the top leg and the bottom leg you would read 240 volts RMS. By using the center tap (common) and the top leg for some of the loads you only measure the current flow and voltage for the top leg in this case 120 volts RMS. The current flow goes out the top leg and in the common then reverses.The voltage goes from 0 to 120 volts RMS to 0 then to -120 volts RMS. That is as referenced to ground.
Any single leg of the secondary could be connected to ground and you would get the close to the same results. If the top leg was tied to ground instead of the center you would read 240 volts RMS from the top leg to the bottom leg and 120 volts RMS from the center to either of the other two legs. The only difference would be reading to ground (the reference point). In this case you would read o volts from the top leg to ground, 120 volts RMS from the center tap to ground, the difference would be reading from the bottom pole to ground which in this case would be 240 volts RMS.