Three-Phase Biaxial Excitation Synchronous Generator (BEGA) Intern-Fault Experimental Characterisation

A comprehensive experimental approach is given, considering a three-phase (star connection) synchronous generator with biaxial excitation (permanent magnets-based flux along the q-axis and dc excitation-based flux along the d-axis) for automotive standalone and wind turbine applications, in terms of intern-turn short circuits. The output power is generated on a resistive load via a diode bridge rectifier. Each phase in the generator is divided into 6 equal parts which allows short circuits to be made with a gap of 1/6 of the total number of turns. The paper presents the synchronous generator behavior at constant load and speed for different excitation currents for short circuits between different number of coils on the same phase, or between different phases. More than that, the paper highlights the instantaneous behavior of the machine for a transition from non-short circuit operation to fully short-circuit operation, in terms of phase voltage and currents, and output power. It was experimentally demonstrated how different percentages of short-circuited coils on one phase or between phases influence the output power.