Loss Definition of Electric Drives by a Calorimetric System With Data Processing

An accurate measurement of power or heat losses of high-efficiency electrical devices is difficult with input and output powers. In the calorimetric method, these losses are measured directly. In this paper, a functional heat loss measurement concept with adequate data processing methods is suggested for heat losses up to 2 kW. Such a heat loss range can be applied to present-day power electronic converters with the rated power of up to 110 kW and motors up to 37 kW. The measurement system does not require a complex mechanical structure or a large footprint area on the measurement site. The concept is scalable to different sizes. New features to the balance type calorimeter data processing are introduced. These include a mass flow correction, a technique to detect the thermal equilibrium, and a method to correct measured heat losses to improve the measurement repeatability and reduce the measurement uncertainty. The measurement uncertainty of the proposed calorimetric concept is 0.4%. Laboratory measurements are carried out both for a commercial frequency converter and an electric motor. These are measured at the same time with two calorimeters. The losses of these devices are measured both by the input-output and calorimetric methods.