1. Preface

The current measurement we used on inductor usually applies LCR bridge. Through auto balancing theory of the bridge, an digitized bridge measures parameters of the inductor (including inductance and quality factor etc.) by applying a high frequency voltage signal on inductor under test. As the AC voltage used for measurement is less than 10V, the current through inductor is also lower than tens mA, and the bridge will measure the inductance parameter under this small signal. This method is usually applied on measurement of inductor component in a small signal analog circuit.

The inductor is known to be a non-linear component, and the current through the inductor would decide the magnetization of the magnetic material in the inductor, and thus establish relationship between inductance value and current. The current LCR bridge + DC bias source measuring method is achieved by overlaying a high frequency small signal on a stable DC current. This traditional method is not only expensive but also complicate to operate, meanwhile it’s maximum current is limited to 200A, which is way behind the development of today’s power electronics products.

With the rapid development of the large power electronics and new energy product, the current rating of power inductor rises day by day, and requirement for power inductor more than 1500A is no longer a news. The engineers today concern for a series of questions: whether the inductance attenuation of the power inductor can fulfill design requirement under high current? Is it saturated and to what extent? These questions are crucial for designing a product aiming for high reliability and low cost.