BEGA-biaxial excitation generator - operation for constant diode dc output voltage with 3,6,9 phases for increased redundancy

This paper presents BEGA in generator mode with three three-phase winding and three diode bridge rectifier dc parallel-connected for full power. BEGA is a synchronous machine with a biaxial excitation: one along the d-axis produced by the dc excitation coils (fed through brushes on contactless) and another one along the q-axis produced by the PM. The low-cost ferrite PMs are placed in the flux barriers, in order to destroy the stator-produced q-axis flux linkage. The investigation is rooted in 4 a pole BEGA with 36 slots existing prototype so that FEM investigation is complemented by preliminary measurements related to power level and quality in faulty conditions.It was experimentally demonstrated (with common and insulated null between all three-phase winding sections) the fault-tolerant characteristics in different fault conditions (either interrupted phases or missing diodes). A clear view of the different fault effects on the harmonic spectrum is presented via Fast Fourier Transform (FFT) analysis.