Investigation of Pulse Excitation in Air-Core Pulsed-Alternator System

Abstract

An air-core pulsed alternator is made of nonferromagnetic materials, which needs very high field current. Self-excitation is usually applied in these systems. This is a positive-feedback progress, which takes tens of milliseconds to reach the desired large field current. The field loss is one of the main limitations of the machine design. This paper presents a new excitation mode, which is the pulse-excitation mode. The main idea is that a pulsed current charges the field coil so that the field coil and the armature coil conduct electricity only for a short time around the main discharge pulse. The field-current pulse is supplied by a pulse capacitor. Generally speaking, the pulse-excitation mode is a combination of pulsed alternator and capacitor. Compared with the self-excitation operation mode, the pulse-excitation operation mode reduces the field loss in each discharge process. This increases the discharge frequency of the air-core alternator pulse-power system. In addition, the repeat discharge-current pulses could have similar peak value. In this paper, the pulse-excitation mode in a pulsed-alternator system is investigated. The simulation results of this scheme are presented. The discharge current, field current, voltage of the field capacitor, and rotational-speed changes are analyzed. Finally, the advantages and disadvantages of this mode are discussed.