Eli5: What’s the difference between a single phase electric current versus a 3 phased one?
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For power coming into the house, we use AC – alternating current. The voltage alternates between positive and negative, following a sine wave (what you imagine a wave looks like).
We talk about waves as having a phase. This just means where in the cycle we start/are. For a sine wave, the start, labelled 0°, is usually when it’s in the middle and about to go up. We label the phase from 0° to 360° because the height of a sine wave is just the height you’re at when you go round a circle anticlockwise from horizontal.
Three phase AC uses three different wires to carry the electricity in, each at a different phase. They are spaced 120° apart. You could think of the extra phases as starting ⅓ and ⅔ along the wave, or as starting 120° and 240° around the circle.
Because maths, a properly controlled 3-phase system has a *total* voltage of 0V at all times. E.g. one wire will be very negative and the other two will be slightly positive, so the voltages all add to 0. This means in theory if you grabbed all 3 phases in one hand, you’d be safe. You might get an injury on your hand, but the electricity wouldn’t flow through the rest of your body and kill you. I wouldn’t recommend testing this…
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