why we use 3-phase supply?why is not 4 or something else?

Answer 1

Three phase power has several advantages over single phase power, including smaller transformer size and weight, and simplified motor construction. Four phase power, which is actually two phase power with the phases in quadrature (90° apart), doesn't really offer any advantage over three phase power but requires an extra conductor. Some experimental work has been done with 6 and 12 phase power, but these have never been put into common usage. When you consider the cost of long transmission lines from the power source, three phase power is the best alternative.

Answer 2

4 Phase Power

Answer 3

here i copied this from howstuffworks.com


Why three phases? Why not one or two or four? In 1-phase and 2-phase power, there are 120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. Four phases would not significantly improve things but would add a fourth wire, so 3-phase is the natural settling point.

Answer 4

Three phases work fine, and there was no need to over-complicate things by generating power in more phases.

If there were any practical advantage, I suppose more phases would be used.

Answer 5

there became right into a power equipment (i've got confidence interior the northwest US) that allotted power in 2 area, ie 0 and one hundred eighty tiers, which required specifically wound vehicles. there became into additionally some vehicles that have been 4 area, ie 0 , ninety , one hundred eighty and 270 tiers. yet all US producing stations now grant 3 area power, ie 0, a hundred and twenty and 240 tiers, and all 3 area vehicles are wound for those ranges. This standardizes vehicles and distribution kit to make electricity undemanding to apply.

Answer 6

there is no four phase supply generation in world.