Analysis and Preliminary Experimental Research of a Multiphase Air-core Pulsed Alternator

The air-core pulsed alternator capable of miniaturization and lightweight has become one of the most potential power supplies for electromagnetic railguns equipped in all-electric vehicles or ships that have strict restrictions on volume and weight. Although the air-core machine has undergone decades of continuous research, a systematic theoretical basis is still in absence, especially for electromagnetic analysis and transient operating analysis. Besides, researchers are less willing to share their latest achievements for the sake of national interests, and the detailed experimental results of this alternator are seldom made public in recent years. In this article, the electromagnetic theoretical analysis, including the analytical expressions of magnetic flux density and inductance parameters, is carried out. Then, a comprehensive transient operating theoretical analysis of four stages is put forward with some typical operating parameters derived. Based on these two kinds of theoretical analysis, the scheme of a six-pole and seven-phase alternator is determined. Simulations are executed to verify the theoretical analysis and prove that the designed alternator can meet the proposed operating targets. Finally, some preliminary experiments for the fabricated prototype are conducted under low experimental parameters. The experimental results indicate that the power electronic devices can work properly, and the self-excitation rectifier takes effect in lifting up the field current. Although the discharge experiment is not carried out under rated experimental parameters, it still makes sense since it reveals the superiority of the prototype in releasing a discharge current very close to an ideal trapezoidal wave to ensure that the projectile can move steadily in its acceleration process.