Three-phase calculation confusion

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Strathead said:
Yes, with respect you said load. Load is amperage. You didn't reference voltage in that question. The voltage sine wave and relationship is completely different than the amperage sine wave and relationship. One is constant the other is cumulative.
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Are you willing to share the correct answer to my perceived question? What degree is V1 at when V1 to V2 is 208.
 
oldsparky52 said:
Are you willing to share the correct answer to my perceived question? What degree is V1 at when V1 to V2 is 208.
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How about I give you a clue. Look at the stationary sine wave that was posted or find one on the internet. Pick any point in time and measure the distance between two phases, then pick any other point in time and measure the distance between the same two phases. What is the result? That distance is the graphic representation of the voltage potential.
 
Strathead said:
How about I give you a clue. Look at the stationary sine wave that was posted or find one on the internet. Pick any point in time and measure the distance between two phases, then pick any other point in time and measure the distance between the same two phases. What is the result? That distance is the graphic representation of the voltage potential.
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If I had the tools to measure that I would have done it instead of asking. Since the sign wave is not linear, I can't measure it with a scale and I have not seen a graph that had enough voltage markings on the Y axis and degree markings on the X axis to make a good guess.

I guess I could try to copy/paste a drawing into a CAD program, but I'm not so sure I'd get the scale correct.

If I could work the formula for the instantaneous voltage on the sine wave, then I wouldn't need a graph. I thought it would be easy to get that answer here, but either I'm just not asking it correctly enough or the answer is quite elusive. Either way, UNCLE!
 
oldsparky52 said:
In the drawing that kwired posted, when V1 is at 90 degrees it is +120V to neutral and V2&3 are both at -60V to neutral (a voltage of 180 between V1 and either V2 or V3). I was just trying to find out where V1 (at what degree) is when the voltage between V1 and V2 is 208V.
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oldsparky52 said:
but either I'm just not asking it correctly enough or the answer is quite elusive.
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60 degrees (30 degrees before V1 peaks.)
 
oldsparky52 said:
If I had the tools to measure that I would have done it instead of asking. Since the sign wave is not linear, I can't measure it with a scale and I have not seen a graph that had enough voltage markings on the Y axis and degree markings on the X axis to make a good guess.

I guess I could try to copy/paste a drawing into a CAD program, but I'm not so sure I'd get the scale correct.

If I could work the formula for the instantaneous voltage on the sine wave, then I wouldn't need a graph. I thought it would be easy to get that answer here, but either I'm just not asking it correctly enough or the answer is quite elusive. Either way, UNCLE!
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I'm sorry, and my point was actually wrong. I assume there is one or two people here who can answer your question. Regretfully, the one person everyone knows could have answered you is Smart$ and he passed last year. Your question is a very deep math question and if I could remember all of my algebra and trigonometry then I think the answer lies there. At any point in time the three add together, ignoring negative numbers to total the same amount so if your reference is A phase, and it is at zero B phase is going up, then B and C are equal and opposite the zero line. go a little further in time and one of those phases is dropping toward zero getting steeper and the other phase is going away from zero getting shallower. At any time though, I am pretty sure the sum of all three is the same.
 
kwired said:
Air handler with MCA of 59 amps - sounds to me like it probably has electric heat strips in it. If that heat can't run at same time as condenser unit then you only have the air handler load to account for for a common supply.
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Strathead said:
Caveat...

Unless the Condensing unit is actually a heat pump.
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If the heat strips can run while heat pump is running.

Most that do run at same time only do so during defrost cycle, technically code doesn't say you can disregard that, reality - doesn't last long enough that it is really much of a problem, compressor might only be drawing half of RLA at the most in many cases as well.
 
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