Development of an air-core cylindrical HV pulse transformer

The structure of an air-core cylindrical high voltage pulse transformer is relatively simple, but considerable attention is needed to prevent breakdown between transformer windings. Since the thickness of the spiral windings is on the order of sub-millimeter, field enhancement at the edges of the windings is very high. Therefore, it is important to have proper electrical insulations to prevent breakdown at the edges and to make the system compact. Major design parameters of the transformer are primary inductance of 170 nH, and output voltage of about 500 kV. The fabricated transformer is 45 cm in length and 30 cm in diameter. The fabricated transformer is tested up to 450 kV with a Marx generator. In this paper, we will discuss design and fabrication procedures, and preliminary test results of the air-core cylindrical HV pulse transformer.