Why 3-phase voltage is 440V instead of 660V?

Answer 1

Three-phase is transmitted at many different voltages but a 440 v 3-ph supply has 440 v between the phase wires by convention and is used in supplying power to groups of houses or small businesses.

The voltage between any of the phases and neutral is 440/sqrt(3) which equals 254 v.

A typical 440 v 3-ph transformer might be able to supply 700 amps, which gives 180 kVA, enough for about 90 houses.

Answer 2

You would use 440 v 3-phase in a large house or business where the need for electric power is more than can be supplied by a normal single-phase circuit.

A very large business needing more than about 700 kVA might use 11 kV 3-phase.
A 3-phase supply allows more power to be used than with a single-phase supply. 3-phase is the usual way of transmitting electric power efficiently. For domestic supplies a street might have a 3-phase supply running along it with each property using one of the three phases.

Answer 3

A standard voltage for 3-phase suppies in Europe is 440 v. That gives a line-to-neutral voltage of 254 v. 690 v is not used, mainly because it is higher than is considered satisfactory because it is more dangerous.

Answer 4

at generation one phase is positive, one phase is negative and another is zero simeltaneously

Answer 5

Because 3 phase voltage is not algebraic sum it is the vectorial sum. Vijaye Raj A.I.E.M.D