3 Phase AC Supply

In single phase supply, 220V is voltage diff. between Line & neutral while, In 3 phase supply there are 3 supply lines phase shifted at 120deg from each other, so net voltage diff. (the phase resultant) between two phases in accordance with phase angle of 120deg is 440V.

However in 3 phase, 4 line systems having 1 neutral also, the voltage diff. between neutral and any of the phase is 220V...

In case of 1Ph supply voltage is measured in between Phase and neutral, but where as in the case of 3Ph supply it is been measured in between two phases of line which differ each other by an phase difference of 120 degrees. So resulting net voltage between two lines which differ each other by a phase difference of 120 degrees always hovers around 440V

In 3 phase power electrical systems there are 3 phase in and 1 neutral because neutral is common for both in and output sources. 3 Phase electrical In used for high wattage expenses.

440v is the line to line voltage, there is 230v for phase to neutral. So both 230, 440 volts is common operating voltage recommended by Indian standard rules. If our application required 660 volts, Just we step up the voltage by suitable step up transformer.