Quote:
quote:Originally posted by BB_TX
Again I will have to disagree, although it may just be semantics.
You can have 50 amps flowing thru line 1. And at the same time you can have 50 amps flowing thru line 2. So at maximum current flow thru both lines at the same time you can have 12,000 watts of power (100 amps x 120 volts = 12,000 watts).
You can't have more than 50 amps flowing thru either hot leg or any wire at any time. And (at any given time) the current flowing into one leg is flowing out the other leg. So in that respect it is not additive. But you do still get the EFFECT of having a total of 100 amps IF you have loads that would draw the maximum of 50 amps from each hot leg at the same time. The 50 amp breaker is a double pole breaker, each pole rated for 50 amps. Since the hot legs are not additive, you can have up to, but not more than, 50 amps flowing thru each pole and to each separate group of loads simultaneously.
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Look at the drawing.
As you pointed out it is AC so one second one end on the transformer is + and the other end is -. The next second that changes. So the current flows thru both breakers at the same time in the same direction.
The power flows between the 2 lines. If you exceed 50 amps anywhere in the circuit you will trip the breaker.
We haven’t been talking wattage at all and if you want to go there then you need also to talk about power factor.
All of the information I have posted came from the text books I just made a typo error. It is a common mistake and I thank you for pointing that out. It is a long course if you study only the AC electrical part 8 hours a day the course takes 2 weeks to finish. It has now been 8 years since I did the last refresher course.
The school I attended for the 2 week course in Tucson had a demonstration panel with amp meters installed in all three lines and as the load was equalized on Line 1 and Line 2 the neutral amperage dropped accordingly until it was no longer readable by the meters being used. The voltage meters wired to neutral remained at 120 volts and the volt meter wired between line 1 and line 2 remained at 240 volts thru the entire demonstration.
The power flows between line 1 and line 2 when the load is equal. The difference between line 1 and line 2 is carried by the neutral.
If this were not the case the neutral wire would have twice the capacity of the wires to line 1 and line 2.
So we play the game with math.
100 amps X 120 volts = 12000 watts
50 amps X 240 volts = 12000 watts
This is simple formula that doesn’t take into account power factor.
Phil P