A Simple Power Loss Evaluation Method for High-Frequency Transformers Based on Surface Temperature Measurement Within Wide Operation Range

Power loss measurement and evaluation form the foundation of loss modeling and optimization. This article proposes a method for evaluating power loss in high-frequency (HF) transformers operating under forced air-cooling conditions, simply based on surface temperature measurement with a thermal camera. A direct correlation is established between power loss and surface temperature, utilizing a simplified thermal network. This method enables the measurement of both total loss and individual core loss and winding loss directly for HF transformers operating within the whole range of normal working conditions. Simulations are conducted to validate the practicality and accuracy of the proposed method. Experiments are carried out on a HF transformer prototype, following the proposed loss evaluation process. The accuracy of the evaluated power loss is validated through HF short-circuit (SC) tests, open-circuit (OC) tests under various excitation waveforms, and loaded tests. Additionally, magnetic cores with an air gap are employed in the loaded tests to demonstrate the significance and effectiveness of the proposed method in evaluating air-gap fringing effects. Error analysis is performed, and factors that impact the accuracy of the proposed method are discussed, aided by simulations.