Studying Three Phase Supply in School

The power distribution of nearly all major countries have accepted 3phase distribution as a standard. With increasing power requirements of instrumentation today even a small physics laboratory requires 3-phase supply. While physics students are given an introduction of this in passing, no experiment work is done with 3-phase supply due to the sheer possibility of accidents while working with such large powers. We believe a conceptual understanding of 3-phase supply would be useful for physics students with hands on experience using a simple circuit that can be assembled even in a high school laboratorys. Introduction Edison’s invention of direct current (DC) preceeded Tesla’s invention of alternating current (AC). However, once there were two possible modes of power available, an inevitable debate on the merits and demerits of the two started that led to what is called the “war of currents”. The inventor’s became adver1 saries with Edison promoting direct current (DC) for electric power distribution over the alternating current (AC). The “war of currents” got so bitter that both inventors lost a lot of money and rumors have it, their Nobel prize [1]. Today the debate is more or less resolved with AC being accepted as the best method for electric power distribution, especially where the power requirement is large. It can be appreciated that since direct current can not be trivially stepped up or stepped down, the same voltage level is transmitted as required by the load. This resulted in large transmission losses. Transmission loss takes place due to heat dissipation along the current carrying wires used for delivering power from generation point to consumer. The initial transmission networks laid were of copper, which is one of the best conductors with low resistivity. Even with low resitivity, since the length of the transmission wires involved are large, they offered finite and non-negligiable resitance. Thus introducing power loss during transmission. Mathematically power dissipated is gien as Pdis = I R = ρ ( l A )