
3-1
3.1 Introduction
AC machines with three or more phases (n ≥ 3) operate utilizing the principle of rotating eld,* which is
created by spatially shiing individual phases along the circumference of the machine by an angle that
equals the phase shi in the multiphase system of voltages (currents), used to supply such a multiphase
winding. Such machines are of either synchronous or induction type. All rotating elds in multiphase
machines, caused by the fundamental harmonic of the supply, rotate at synchronous speed, governed
with the stator winding frequency. When the rotor rotates at the same speed, the machine is of syn-
chronous type. When ...