3-D FEM Analysis on Electromagnetic Characteristics of an Air-Core Pulsed Alternator

In pulsed power supply for electromagnetic launchers, air-core pulsed alternators have obvious advantages to enhance the power and energy densities with a compact and lightweight structure, and it is gradually to be the prime candidate for pulsed power supply. Compared with conventional machines, an air-core pulsed alternator will supply large amounts of energy over millisecond time with a huge current as high as 1 MA and a high voltage reached several kilovolts. Since the short history of the air-core pulsed alternator in China, the related theoretical research is not enough and the fabrication experience is absent. At present, research has shown that the performance of the air-core machine cannot be evaluated by the 2-D method due to the nonexistence of ferromagnetic materials, and it is very necessary to carry out the 3-D analysis by a finite-element method (FEM). This paper will present a 3-D model of the machine according to the accurate geometric size, and the model is used to develop electromagnetic analysis by the FEM and a transient simulation about the no-load EMF is carried out too. In order to understand the mechanism and process of electromechanical energy conversion, it is obviously important to figure out the magnetic field distribution in the machine. Meanwhile, in order to evaluate the strength of the windings, the calculation of electromagnetic forces and torques is developed when the machine drives the electromagnetic rail gun with a current of 1 MA.