Investigation on phase angle mismatch of multiple air-core pulsed alternators

As the energy level requirement increases in pulsed power applications, it becomes necessary to utilize multiple air-core pulsed alternators discharging into the load. The counter-rotating pulsed alternator pairs can also compensate torque and gyroscopic effects of pulsed alternators. The whole work process of multiple pulsed alternators can also be divided into self-excitation process and discharge process. In the self-excitation process, the alternators work separately and the effect of phase angle mismatch is ignored. However, in the discharge process, the armature windings are connected in series or in parallel to share the output voltage or current. The phase angle mismatch between the alternators will affect the waveform of the output current of each alternator in discharge process and the rotational speed after discharge process, so the phase angle mismatch becomes a key factor of the system. Phase angle mismatches are introduced in this paper to see how it affects the work process of multiple air-core pulsed alternator systems. Based on some simplifications, the analytical analyses are performed. As to two alternators connected in series, the phase angle mismatch will not cause greater damage to the discharge switch. However, at the end of discharge process, only one alternator acts as a generator and the other alternator as a motor. As for two alternators connected in parallel, the maximum discharge current of the slave alternator is larger than the one of the master alternator. The phase angle mismatch will also lead to bad results for the torque and gyroscopic effects compensation after discharge in both series and parallel connection mode. To verify the conclusions of the analytical analyses, some simulations are performed on two identical pulsed alternators except for their phase angle. The results and conclusions of the analyses and simulations can offer guidance for the design and optimization of multiple air-core pulsed alternator systems.