ABSTRACT
As shown in Chapter 3, synchronous machines (SMs) are characterized by ac multiphase winding currents in the stator, and dc (or PM) excitation or magnetically salient (reluctance) passive rotors. These are basically traveling field machines in which both stator and rotor fields are rotating “synchronously” at the rotor electric speed, ωr:
ω1 = ωr = 2πp1n1; n1 = f1p1 (6.1)
where ω1 is the stator frequency p1 denotes pole pairs
There are also unipolar rotor-position-triggered or ramped-frequency stator-current pulse multiphase machines with reluctance (and eventually with PMs also) rotors that have a stepping stator field whose average speed is equal to the rotor speed. These are called stepper machines when the current pulses are initiated at a ramping reference frequency independent of the rotor position, or are called switched reluctance machines when the current pulses in each phase (one or two at a time) are rotor-positiontriggered.
