Electromagnetic shields of the air-core compulsator

Air-core compulsator is a specially designed generator capable of delivering high current pulses to a low-impedance load, such as the electromagnetic railgun. Due to the absence of ferromagnetic material, the field strength in air-core compulsator can reach to 4~6 T. Therefore electromagnetic shields are required to protect the surrounding operators and instruments from exposure to high magnetic fields. This paper investigates the design methodology of the shield as well as its influence on the performance of the machine. A dynamic model is built to analyze the shielding effect and its performance trade-offs of a reference compulsator. The result indicates that the effect of the eddy current shield is much better than the magnetic shield using ferromagnetic material, due to the high frequency and the magnetic saturations. The magnetic field can be completely screened inside the conducting shield, at expenses of some electrical, mechanical, and thermal performance. Since the eddy current density is sensitive to the location of the shield, the influences of the conducting shield are parametrically analyzed. By using the electromagnetic and thermal coupling field link, the temperature rise of the shield is also calculated. Analysis results can provide the theoretical guides for the shielding of the air-core compulsator investigation in the future.