Design of Current Transformer for in Situ Current Measurement of Discrete SiC Power Devices

The accurate measurement of the voltage and current waveforms during the high-speed switching transition of the discrete silicon carbide (SiC) devices is necessary in order to estimate the switching loss with reasonable accuracy. The current measurement is usually more challenging, as it requires the insertion of a current sensor into the testing board. The existing current measuring methods are still limited by the drawbacks, such as low current rating, low bandwidth, and bulky size, for installation. As a result, an in situ current measuring method with convenient installation as well as sufficient current rating and bandwidth are proposed in this article, which consists of a first-stage custom-made current transformer (CT) and followed by a second-stage current probe (CP). By having the custom-made CT, the size of the CT can be very compact and requires little space provision in the testing board, which preserve the measuring accuracy. A comprehensive analytical model with bandwidth, current gain, and saturation current as design parameters is developed. Based on the developed model, three CT designs using different magnetic cores are fabricated and their performances are also experimentally validated. © 2020 IEEE.