Precision calorimetry for the accurate measurement of inverter losses

High precision calorimetry permits the direct measurement of losses in power electronic systems. This paper describes improvements to the design of a double-jacketed, closed type calorimeter in order to make these measurements. Calibration tests have confirmed that the new design can measure losses to an accuracy of better than 0.5 W in 200 W. This calorimeter has been used to verify the accuracy of models for inverters for use in variable speed drives for domestic appliances. Verification has been undertaken at a range of switching frequencies and confirms the ability of the models to predict inverter performance without recourse to physical prototypes.