On the Electrical main board at home,there is a rotator selector to choose between 3 lines. The guy who installed it said we could switch the line when power goes down on one and said we have ‘3phase’ power.Could someone explain what this arrangement is,I’m confused by what the guy said.

Question

I don’t necessarily understand how it can be termed 3 ph power,because we don’t simply get 3ph to homes as we please,right? Moreover we don’t have any heavy machinery that might even require it. Could someone explain how this arrangement works? Is it just switching between feeders like in a ring fed arrangement of the power system? Or is it actually 3ph power(?)

In: 4

Answer 1

Generators make electricity when they rotate a magnet next to a coil. It generates electricity in one direction as the magnet passes by the coil one way, and in the other direction as it passes by the other way. But it generates nothing when the magnet’s head is away from the coil, and as generating electricity creates a force slowing down the spinning magnet, the force increases and decreases as the magnet spins.

With the forces involved in large generators, This uneven load would create vibrations that would destroy them.

If you put 3 generators – 3 sets of coils around the same magnet – this evens out the load. When one coil isn’t generating power, the other two are, and when one is at its maximum, the other two are generating less. The 3 independent coils create 3 independent supplies of electricity, each having voltages that peak at different times. These are the 3 phases of an electricity supply. You can pull power from them by connecting your device between a phase and neutral, or connecting it between different phases.

But you are right – 3-phase supply is unusual in residential areas. You normally have to pay extra, and people only do this if they have large equipment, especially large motors, that run more smoothly when using a 3-phase supply, for the same reason that generators do. Your sparky decided that, as you already had a 3-phase supply – perhaps the previous owner had a large device that used it – he’d give you the option of switching your supply between the phases. Sometimes one (or, more commonly, 2) phases stop working, and at those times it would be nice to switch your house to the working phase. But your power company might not like this – they spend some time arranging things to balance the load on the phases.