why 3 phase electricity instead of 4 or 5, etc?
In: 1
The first motor to be controlled in speed and direction of rotation needed 3 sin waves at 120 degrees offset.
This system allows you to power heavy machinery with minimal control devices, and can turn the machine one way or the other on demand. The basic form is controllable with a single switch fwd-off-backward.
Generation of the phases is as easy as using them. You make an alternator with 3 sets of coils at 120 degrees from one another.
Adding phases does just make it more bulky or complex with no benefits.
Imagine the grid was made around the concept of “a century ago factories” using this 3 phases to move everything, with rudimental controls.
3 phases do not have any particular downside for all the other applications like lighting, or powering devices with their own transformers like PC, radios, printers, and home electronic things like ovens, blenders, toaster. There was never a need to change the system. If you don’t need 3 phases, you just take a single one and use it. For example for houses. Let’s say there’s 300 houses in your area, the company will connect 100 houses to each phase and call it a day. As long as the grid has similar loads on each phase, everything works.
So it works, it’s as simple as you can get it to be in order to cover all possible applications.
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