An Equivalent Circuit for the Salient-Pole Synchronous Machine

A time-phasor diagram is generally used to display amplitude and phase relationships between currents and voltages existing in an electrical network. However, although the simple equivalent circuit corresponding to steady-state operation of the round rotor synchronous machine and its associated phasor diagram are very familiar, the phasor diagram of the salient-pole machine is presented in many undergraduate texts without any attempt to specify the displayed quantities on a related circuit diagram. An equivalent circuit for the unsaturated salient-pole synchronous machine operated under balanced, steady-state conditions is derived from a consideration of the voltage and current equations implicit in the phasor diagram. Further equations are developed such that a knowledge of the terminal loading conditions of the machine, together with its armature resistance and synchronous reactances, enables the equivalent circuit parameters to be calculated. The unexcited synchronous reluctance machine is considered as a special case.