Junction Temperature Estimation Via Plug-In System for the Design Validation of IGBT Industrial Power Converters

In the design process of power electronics converters, the power semiconductors thermal modelling is one of the most critical tasks. An accurate estimation of the junction temperature allows the validation of the converter design and also the calibration of the thermal models during prototyping. Therefore, this paper presents a straightforward method to estimate the junction temperature directly on the target converter using a plug-in measurement system. The estimation is based on the IGBT on-state voltage measurement under high current with a dedicated sensing circuitry externally connected to the converter under test. This solution is specifically designed to fulfill the needs during the prototyping process and design validation since allows a fast and reliable monitoring in all working conditions of interest and the sensing circuitry does not affect the normal operation of the converter under test (CUT). The acquisition circuitry and the calibration procedure are described and tested on a 68 kVA IGBT industrial three-phase inverter. The experimental results obtained on the target inverter prove that the proposed design validation based on the implemented estimation of the junction temperature provides better results than the conventional design methods based on thermal models implemented in simulators.