Investigation on Cascode Devices for High Frequency Electrical Drives Applications

In the last years a widespread development in the market of electrical drives employing high-speed electrical machines has occurred in various industrial fields, due to the extremely high power density that can be reached. Nevertheless, to maintain output power quality without using bulky filtering networks, DC-AC converters should be controlled by means of higher PWM switching frequencies. New switching device technologies, such as Field Effect Transistors based on SiC and GaN, are therefore gathering momentum in order to comply with the higher working frequencies. To operate under high frequencies and at the same time at high voltage levels, alternative circuital configurations for switching power devices are also investigated. The cascode structure is particularly appropriate for those applications. In this paper, after a detailed overview of the most recent state of art in the field of cascode devices, a typical application of three phase inverter will be investigated using some cascode-based solutions, for a 400 Hz modulation frequency. An experimental prototype concerning a single-switch DC-AC is presented in order to investigate the results given by a cascode structure