Analytical Investigation and Scaled Prototype Tests of a Novel Permanent Magnet Compulsator

Compensated pulsed alternator (compulsator) is one of the most popular choices of pulsed power supplies for fusion reactors, high-power pulsed lasers, and hypervelocity electromagnetic launchers because of its high energy density and power density. In general, external excitation in the form of self-excitation or pulse-excitation is adopted in compulsators together with iron core or air core. This results in heavy, bulky components and a system that is more complicated and less reliable. In this paper, a novel compulsator that is excited using a permanent magnet (PM) and is equipped with an iron-core or air-core stator is proposed. An excitation converter or brush-slip ring system is not needed in the novel system, which consequently makes it more reliable, less massive, and less voluminous than the external excitation machines. In addition, the novel PM compulsator acts not only as a pulsed alternator capable of delivering high-power pulses but also as a brushless PM dc motor that can be employed to charge the energy storage rotor. Thus, no external driving motor or gearbox is needed in the pulsed power system, which makes the system integrated and compact. In this paper, analytical models for the air-gap magnetic distribution, the back electromotive force, and the pulsed current waveform of the machine are deduced. A PM compulsator is designed and analyzed, and a scaled prototype of the PM compensated pulsed alternator is fabricated and tested. The actual output voltage waveforms and pulsed-current waveforms are sampled and compared with the predicted ones, which clearly demonstrate that the design of the PM compulsator is feasible.