Considerations on the development of an integrated electric inverter for high temperature applications

Abstract

The realization of integrated solutions for electric machine drives is a way to achieve higher space utilization in industrial and transportation electrical power applications. In some cases, limited space affects heat dissipation and the performance of a cooling system, so harsh operating conditions, i.e., high ambient (or cooling) temperature, are a possible additional requirement for integrated drivers. This research investigates in detail the design of some essential or sensitive parts of IMD, highlighting their behaviour under a high-temperature environment. An initial selection of switching power devices is a cornerstone of the inverter design that determines a number of crucial electrical, thermal, and mechanical parameters of the final assembly. Traditionally power modules or custom-designed power devices are the preferable choices for such challenging power electronics applications. An alternative approach based on the parallel connection of discrete MOSFET is underestimated by researchers and is less popular nowadays, although it can offer some valuable advantages. This work presents a comparative analysis of different power devices' packages with a generalized evaluation algorithm focusing on thermal and mechanical aspects in addition to conventional analysis of devices' electrical characteristics. The proposed method helps evaluate the range of feasible power density for PE and the drive itself. The results could give reference figures to demonstrate the capabilities of all popular power packages of novel SiC MOSFETs in the 2-level 3-phase inverter. In selecting power devices, special attention is paid to highlighting possible trade-offs between losses, junction temperature, and occupied volume. Another comparison analysis considers the characteristics of different capacitor materials under various operating conditions and evaluates the required volumetric parameters for DC-link capacitor of the inverter. Several technical challenges related to the adoption and balancing of MOSFET parallel connection are discussed in the thesis. The possible protection of paralleled power devices against the crosstalk effect is studied in detail with a proposed simulation model of the gate driver circuit. Limitation of typical clamping methods if applied to parallel devices is demonstrated. The modified gate driver with a reduced current clamping path generates a lower voltage pulse and enhances the protection against spontaneous turn-on; its efficiency is verified by model simulation and experimentally. New thermal protection for current sensors, providing acceptable conditions up to 130C degrees of ambient temperature, is described and tested.

Date of Award	Jul 2023
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Giampaolo Buticchi (Supervisor), Michael Galea (Supervisor) & Pat Wheeler (Supervisor)