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Three-phase electricity explained

Vilnis Vesma's picture
  • Member since 2021
  • 11 items added with 5,747 views
  • Jul 23, 2021

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The kitchen table-top talk uses a hydraulic model to explain the principle of three-phase electricity.

Bob Meinetz's picture
Bob Meinetz on Jul 23, 2021

Brilliant, Vilnis!

I never understood "voltage", "energy", "power", and "current" until an acquaintance sent me a description using water as an analogue. It explained electricity, very much like water, behaves like an incompressible fluid; that voltage is analogous to water pressure; that energy is analogous to the quantity of water that has accumulated in a bucket being filled by a hose; and that power corresponds to the amount of water flowing through the hose, multiplied by its pressure. By picturing electricity as water, suddenly everything fell into place.

I can imagine the challenge of working with water, however, to assemble your demonstration. Pushing/pulling water through a hose with syringes involves much more friction, or "resistance", than pushing/pulling electricity through a wire. Water can freely leak into the surrounding environment; electrons, not so much.

Much as a power plant uses a huge wheel with magnets to pull electrons back and forth as it rotates at a precise velocity, you've constructed a wheel behind your board to do the same.

One of the most remarkable properties of multiphase AC is that at any point of the rotation of the wheel, the sum of currents flowing through the three conductors is zero. In a theoretical resistance-free circuit, you could connect the ends of the three conductors together, give your magneted wheel a spin, and it would spin forever, electrons flowing in one direction exactly cancelling those flowing in the opposite direction.

Similarly, if you connected your three tubes together to a single syringe at their opposite ends, the syringe would move neither up nor down as you turned the wheel behind your board.

Vilnis Vesma's picture
Thank Vilnis for the Post!
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