MOSFET Selection for a 18ka modular power converter for HL-LHC inner triplet

Abstract

The upgrade of the Large Hadron Collider (LHC) at CERN towards the High Luminosity-LHC (HL-LHC) presents different challenges, among them, the upgrade of the power converters associated to the inner triplet magnets to reach the required rated current of 18kA. In order to reach this current and to accomplish the stringent requirements associated to this kind of application, even under a fault scenario, redundancy and modularity are foreseen in the converter design. Consequently, the development of a 18kA/±10V power converter built from 10 parallel-connected sub-converters, each consisting of M modules, is carried out. Additionally, due to the converter being installed in an underground gallery, most of the heat must be extracted by using a water cooling system. Therefore, the reduction of power losses and an appropriate thermal design become key factors. These requirements, together with the large number of devices associated with the parallelization-based modular system, determine the choice of switching semiconductor devices as an important aspect in the design of the converter. This paper presents the process carried out for the choice of semiconductor devices based on analysis of power losses, thermal behavior and integration complexity. In this process, multiple variants in terms of semiconductor, number of modules, parallelization of devices, and switching frequency are considered. The proper operation of the selected device was verified on a 2kA sub-converter prototype based on the interconnection of 9 MOSFET based modules.