Transient Thermal Impedance Characterization of New High Power Press Pack Diodes

Diodes are known as a critical component in power electronics and industrial applications due to their ability to handle high voltages and currents. To optimize their design for high-voltage and high current operations, it is important to ensure their reliability, especially with regard to thermal aspects. In this article, simulations were performed to investigate the thermal resistance and transient thermal impedance of a diode with blocking voltage of 2800 V and a diameter of 46 mm copper pole by electrothermal modeling. Thermal parameters such as resistance and capacitance are calculated and an electrical equivalent circuit, the Cauer thermal network, is developed in PSIM. Furthermore, the Cauer model is transformed into a Foster model. Curve fitting method is used to extract thermal parameters from the thermal impedance curves through non-linear regression in MATLAB®. Using the derived resistance and time constants in Foster network, average current of a device may be predicted at different pulse durations and shapes. Moreover, experimental measurements were carried out to validate the thermal resistance for the investigated diode. Finally, a comparison with analytical curve also confirms the effectiveness of the approach.