How three phase math works (277 + 277 = 480?)

This is a quick run-through of how three-phase math works.

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[toddnelson]

I've been a licensed electrician for 15 years. Only recently have taken my career a lot more serious. Ive always root 3 277 to get explain the answer. But never actually spent enough time getting down to the real answer it just worked to get wire size or over current protection. It's cool to know the things others think they know but actually don't.

[mikol.douglas]

Excellent! Love the short, but explanatory videos. I first learnt the 3 squared method, so it’s good to hear this put another way.

[oBseSsIoNPC]

What I found so far to make this easier, is to consider the 360◦ : 3 = 120◦ (phase shift) right?
So WHEN EVER YOU MEASURE FROM LINE TO LINE (PHASE TO PHASE) you use the square root of 3 and multiply the peak voltage. So 277V * (√3)=479.77807369V
It is the magic number that makes life so much easier.

[lime]

Thank you so much for this video..kept asking my teachers how this worked ans they couldn't explain. I appreciate it 3 years later🙏🙏

[mcheek]

I just posted your link to two of my Facebook pages. I think my friend's and coworkers will appreciate your style and method of explaining electrical systems. Most of the younger technicians seem eager to learn, yet lack the basic math skills they should have been taught in secondary schools. This may be due to lack of emphasis on real world problems these students will certainly face, or curriculums which shifted from math and science to social and less structure oriented subjects.
To the point being though, I can appreciate your time and effort spent compiling this series as well, I am sure, as many others who watch this series of videos. Hopefully you will find that your work here has paid off in ways you are not even comprehending yet.
One thing I always made reference to when questioned about how electricity worked was to say it (electricity), is the closest thing to true magic which exists in our physical realm. Clergy and electricians are much alike in that we both work with (for) something we never really see, yet can certainly feel. If we ask it to help us and obey the set rules, we are rewarded for our efforts. If we stray away from the laws we know we should strictly follow, then it is only a matter of time before we pay a penalty for our mistakes. When all goes as we planned, our FAITH tells us that everything is going to work and our work is done. So we tend to take more time to learn more, and try understanding this thing we cannot actually see, but trust it will allow us to manipulate for the good of our society and the needs of our structures we built.

Hopefully this makes a little sense. Thanks from an old crusty electrical/electronics guy here.

[j.t.johnston]

Love the video. I've always understood why it was 480V but never saw anyone prove it with the vector math. Thanks.

[robertgift]

Well done! Thank you. I would show the 3 sine waves on a graph and show the voltages at various points from one sine wave to another.

[MrRyanSchneider]

Thanks for the refresher. It has been years since I first learned this. I am glad it still works! Haha

[juans]

I am retired now, but I truly enjoyed working with three phase, wye and Delta configurations. Good presentation.

[ethanlamoureux]

I suppose if you want to get technical or you really need to understand the math behind it, you can use all these details. But I hate math and love to simplify things to just the bare essentials. So I would probably say, you can’t simply add two voltages on different phases because they’re 120° out of phase, and thus are never equal at the same moment. For instance, when A is at 277, B is at 203.
To calculate the voltages you can just multiply or divide by the square root of three, 1.732.
120 * 1.732 = 208
480 / 1.732 = 277

[jens]

Great video. Studying for my professional architect licensing exams, and the detailed math explanation is actually very helpful as I am tested on multiple disciplines, including electrical, on my exams. Your breakdown of the math on this simple 3-phase diagram is very applicable to some of the structural engineering portions of my exams as well. Thank you!!

[wagabira]

I'm a level 3 electrical student and this is really helpful. Thanks a lot

[GH-oijf]

Because of the particular angles involved, the square root of 3 can be derived easily from geometry without resorting to trig functions.

[AudioJunkie]

I love the internet! Thank you for a clear explanation!

[MatadorM]

Thanks, this was an awesome simple explanation.

[aaronarellano]

@All viewers. Skip to t=6:00 min and stop watching at t=6:26. That's the sum of a straight fwd subject... Root3..

[factor]

Clear and concise explanation. Thank you.

[farmerdave]

You cannot directly add phase voltages because they do not happen at the same time.

[ericstandefer]

In the field, or on a test,  for a quick calculation just multiply 277v by the square rot of three (1.732) = 480, or 120v times the square root of 3 = 208.

[connerredmond]

If you come from a math background you can always use law of sine/cosine to determine the hypotenuse or in this application, line to line voltage.