what is 3 phase power? How does it work? How does it differ from 1 phase power that most residentials have? Why isn’t 2 phase power as popular?

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It helps to think about electric power as “potential”. What does this mean? Well let’s say you have two buckets connected with a hose. When one bucket is full and the other is empty the water will flow from the full bucket to the empty. To use the power, you let the flow of water do your work, for example spin a water wheel.

In the power grid, we have alternating power, meaning which bucket is the “full one” varies 50 or 60 times per second. The same potential is there, just in opposite direction. (The water is flowing between the buckets, but in alternating directions).

When you have 2 buckets, you get one “phase” (hose). If you add one more bucket, now you get 3 phases, one between each pair of buckets.

Instead of varying back and forth between 2 buckets, it now varies between 3. One is full, one is half full and one is empty. That means that you will have 3 hoses with flow in different directions to drive your water wheels instead of just one.

3 phase power is preferred because it applies a constant torque to a motor and has no current flowing through the neutral when the load is balanced. With single or two phase power the amount of power being transfered to the load varies with time which puts more strain on rotating machines and is less efficient. You can achieve the same thing with even more phases, but there’s no benefit, only added complexity.

Alternating current has a current and voltage that change amplitude and direction over time. It is easy to get out of a generator and you can easily change voltage with a transformer. A higher voltage means a lower current at the same power. if the current is lower the losses in a electrical conductor is lower and you can more efficiently distribute electrical energy.

The number of phases is the number of wires you have where a change in voltage at the same rate but not at the same time

Look at [this image](https://www.electricaltechnology.org/wp-content/uploads/2021/11/Why-3-Phase-Power-Why-Not-6-%CE%A6-12-%CE%A6-or-More-Phases-for-Transmission.png) with 1,2, 3 and even higher phase currents. When the curve passes through zero there is no power at that time. When it is higher or lower the power depends on the side from the zero line.

If you consider the total power of all phases 1 phase to from max to zero. 2 phase to from max to around half of max. But for 3 phase it is always quite high, it never goes below 85% of max. That results in a more even load on generators and electrical motors. That is why 3 phase is in use it is more balances. More phases would make it even smoother but add a lot of extra wires and cost and it is not needed for the power grid.

If 1 or 3 phase is most common in the residential application depends on where you live on Earth. I have always had 3 phases of power where I live both in the apartment and stand-alone house. The only device that had used all 3 phases was the stove/oven it run on 400V 3-phase AC fused at 16A for a total power of 10.4kW. If you have 1 phase that is only 230V you need a wire that can handle 45 amps it would be very tick and hard to handle. But the load of other devices is spread out between the 3 phases. When direct electrical heating was used the radiators were spread out over the 3 phases

If you have 1 phase or split-phase like is common in Noth America what you get is a single phase from the 3 phase grid. The load is spread out by h

Think of two kids on a see saw. They’ve got it it hooked up to some gears turning the crank on an ice cream machine. The more they seesaw up and down, the harder it is to crank the Mach. The cream resists being turned

Now add two more see saws with two more kids each. Now it’s much easier and they can make ice cream faster and easier.

3 phase power is a bit like that. The oscillation of amperage through wire is like 3 sets of seesaws cranking on a single shaft or ice-cream machine.