High Performance Current Sensor Utilizing Pulse Magneto-Impedance in Co-Based Amorphous Wires

A pulse magneto-impedance noncontact sensor, was developed to detect small currents and subsequently the leakage current between two current carrying conductors. The sensing element is composed of Co-Fe-Mo-Si-B glass coated amorphous wire, placed between two μ-metal washers, which allows a simple differential arrangement, due to field symmetry and shielding against environment fields. High frequency excitation was realized by subjecting the wire to a sharp pulsed current provided by a micro-controller. The use of a micro-controller to drive the sensor allows an efficient and programmable way to establish optimal excitation parameters (pulse duration and periodicity) for high sensitivity of small magnetic field detection. There is also a potential of further improvements due to real-time digital filtering, data manipulation and the provision of a closed loop system. In an experiment simulating the leakage current, a resolution of less than 1 mA for a carrier current of few amperes was achieved, which is well below typical fault current levels of about 10 mA.