Certain Design Aspects of Single-Winding Three-Phase Inductor Alternators

Abstract

Based on mathematical analysis, this paper points out that restrictions in stator/rotor slot combinations for optimum output of a conventional inductor alternator are not applicable for one with a single winding for both dc excitation and output. Design considerations for the latter are discussed, and it is demonstrated that its performance is superior to a conventional double-winding inductor alternator in all aspects. Test results on a number of experimental machines fully support the theory. Symbols B = no-load air-gap flux density (Wb/m2) f = frequency of generated voltage (hertz) It= field current (amperes) K = pitch factor Kd = distribution factor I = length of the armature core (meters) 2n = coils in series per phase N = rotor speed, mechanical (rad/s) Na = turns per coil pi = rotor teeth PO = average permeance variation due to rotor slotting (Wb/m2 /At) P = half Amplitude of permeance variation due to rotor slotting (Wbhm2 /At) Pm = exciting pole number Pg = generating pole number PAM = pole amplitude modulation PSM = phase-shift modification r = stator bore radius (meters) t = time (seconds)