Calorimetric loss measurements and optimization of high power resonant converters for pulsed applications

This paper considers the calorimetric measurements of losses and the optimisation of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10 %, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms to 2 ms) of RF tubes when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high frequency power supply. The main aim of the work reported here is to calorimetrically monitor semiconductor losses and to experimentally optimise the value of turn-off snubber capacitors across the devices. The paper provides an overview of the technology and design used on the test rig prototype under study. Experimental results and semiconductor losses obtained through calorimetry will be provided to validate the effectiveness of the proposed techniques.

Introduction

Traditional current generation power supplies in use for high-energy physics accelerator systems are based upon 50/60 Hz, line frequency technology that demands large transformers, filters and capacitors in order to satisfy the specific application requirements. The large growth of current applications for radar and heating using cavity Magnetron/Klystrons has pushed the search for novel “long pulse (1–2 ms)” modulators with reduced size. Low stored energy, high efficiency and high power quality at the utility supply are important requirements for modern pulsed-power modulators.