Why Three-Phase Power?

Minimum number of phases to create an balanced and hence efficient rotating magnetic field (2 phases are minimum, but they are not balanced and a bit less efficient)

GA, but the system is overloaded and not accepting votes at the moment.

yes but why not 4,5?

Minimum number of phases

why there is no execeptional case used anywhere in world like 4,5 phases

please go back and search in cr4 electrical engineering section, it had been discussed sometime ago.

There is another important factor which is "the economic cost" of the three phase power systems, as when you design an electrical system or layout, then you take into consideration the following main factors:

- The system efficiency.

- The proper cost of the system.

Also another factor (as I think) which is "the atmospheric issues".

Thanks...............

My vote is that this is probably the second most asked question in this forum; maybe 50 times in the last 4 or 5 years?

There is an article in Wikipedia on three-phase power.

Dear Mr. Luv123,

During my 2nd year Engineering College Study days, before branching to civil, electrical, mechanical, mining and electronics, our Professor has taught that " FOR A GIVEN QUANTITY OF CONDUCTORS, POLY PHASE SYSTEM WILL CARRY or TRANSMIT/HANDLE MORE POWER than in SINGLE PHASE and HENCE LESS CURRENT and I^2R LOSS, WILL BE LESS.

The power transmitted by POLY PHASE will be N^0.5 (i.e. Sq.Root of N, where N is the number of phase used). We can have as many as 7, but and thus, Power transmitted/handled will be 7^0.5=2.645 times more than the power transmitted/handled by a single phase system. But cost will be very high and construction of alternator, motor windings will be very difficult.

Three phase is the most economical one where the power transmitted for the given material is 3^0.5 = 1.732 times more than single phase system - for the given quantity of the conductor material.

But I am a Mechanical Engineering Graduate and our other CR4 MEMBERS can give their views and answer to this subject.

Thanks,

DHAYANANDHAN.S