Fast high-temperature (250 °C / 500 °F) isolated dc and ac current measurement: Bidirectionally saturated current transformer

Abstract

In an increasing number of application areas and industry sectors, such as the automotive, aerospace, military or oil and gas industry, a trend towards higher ambient temperature rating from 85 °C upward for electrical machines and power electronic converters can be observed. To reduce the impact of high ambient temperatures on the power density, the interest in power electronic converters with SiC power semiconductors operated up to a junction temperature of 250 °C rises. The control of power electronic converters typically requires a precise, fast and robust current measurement. Analyzing current measurement concepts from the literature reveals that there is a lack of a current measurement systems, that are galvanically isolated and are able to measure dc and ac fast at high ambient temperatures of 250 °C. In this paper, a current measurement concept of a bidirectionally saturated current transformer is presented, that is able to measure dc and sinusoidal ac up to 1 kHz and 50A at an ambient temperature of 250 °C with an relative error of 2.6% and less than 0.5% after initial calibration. Furthermore, a prototype is designed, built and used for experimental verification of the concept.