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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 upwards 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. However, analyzing current measurement concepts from the literature reveals that there is a lack of measurement systems, that are galvanically isolated and able to measure dc and higher frequency ac currents 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 50 A at an ambient temperature of 250 °C with an relative error of 2.6% and less than 0.5% error after initial calibration. Furthermore, a prototype is designed, built, and used for the experimental verification of the concept.