Calorimetric Power Loss Measurement for Highly Efficient Converters

The electrical determination of power losses by measuring the input and output power can reach sufficient accuracy for DC-DC converter systems, if well calibrated voltage meters and shunt resistors are applied. However, it is difficult to determine the power in AC-systems, especially with harmonics, due to phase-errors in the electric measurement. In addition, the electromagnetic interference (EMI) of switched-mode power supplies can disturb the electric power measurement. In this paper, the calorimetric determination of power converter system losses resulting in a high accuracy and which is almost immune against EMI phase errors, is described. The closed-type calorimeter is realized with a double-jacketed chamber which enables the power loss measurement between 10 W and 200 W for power converter systems of several kW. The resulting deviation of the implemented measurement system is less than ±0.4 W, or ±0.05% at full load conditions (several kW), respectively, over the entire measurement range.