Loss Analysis of Air-Core Pulsed Alternator Driving an Ideal Electromagnetic Railgun

The pulsed power supply based on air-core pulsed alternators, with advantages in terms of miniaturization and lightweight, has been a preferred power source for electromagnetic launch (EML) systems in all-electric vehicles or ships. However, when an air-core pulsed alternator is used to drive the electromagnetic railgun, the bulk of the inertial energy storage converts into energy losses. These losses not only reduce the efficiency of the system but also cause temperature rising of the alternator, leading to a limit on its repetitive output performance, affecting the performance of the electromagnetic railgun, and ultimately, the alternator's volume and weight will also increase. Therefore, it is necessary to develop research relating to those losses. In this article, the operation principle of the EML system is explained first, and four typical operating stages are described. Then, the influence of the rotor eddy current on the performance of the alternator is analyzed. After that, the various losses generated in the pulsed power supply system are analyzed in detail. The eddy current losses are obtained from simulation. The copper losses and switch losses are calculated by formulas derived in different stages and different members. The formulas of windage and mechanical losses are obtained too. Based on these analyses, losses can be calculated by the parameters of the EML system or derived from a cosimulation model. Also, the influence of alternator parameters and structures on losses is studied. Finally, a seven-phase six-pole air-core prototype is introduced, and the windage and mechanical losses are tested on the prototype. Moreover, the cosimulation model of the EML system is built, its losses are evaluated, and the efficiency of the EML system is derived.