Two-Phase Alternator with DC and AC Stator Excitation 2008-01-1448
A two-phase alternator consists of two one-phase generators. The phase of the two output voltages of the alternator is shifted 90 degrees. The alternator rotor has a salient pole configuration without coils. Two generators are mounted in the stator slots inside the alternator stator. Each of the generators consists of one winding for excitation and one output winding for voltage generation. For generator excitation, DC or AC current may be used. For AC excitation, the direction of current flow is changed as a function of the rotor position. If three one phase generators are used with a 120 degree output voltage phase shift, then a three-phase alternator can be built. The two-phase alternator has simpler construction and less parts than a three-phase alternator and is consequently easier to fabricate and maintain. This paper presents experimental and the field circuit calculation results of two-phase alternators with DC and AC stator excitation. The computations have been carried out for magnetic flux and electromotive force produced. Under the same conditions, AC generator excitation produces the same magnitude of the output voltages as DC excitation and halves the voltage frequency. The results of field calculations enable determination of the internal inductance and resistance of the alternator windings and calculation of the alternator load characteristics. The simulation data is confirmed on an experimental prototype alternator model.