A Coreless Electric Current Sensor With Circular Conductor Positioning Calibration

This paper presents a novel coreless current sensor unit for measuring electrical current of circular conductors. The proposed sensor unit consists of three magnetic field sensors and a microcontroller unit (MCU). The new sensor unit does not need a bulky magnetic core necessary for magnetic field concentration, and can be used in the same way as conventional current transformers (CTs). An algorithm is developed to calibrate the outputs of the magnetic field sensors (e.g., Hall effect integrated circuits (ICs) with respect to the relative position of the current-carrying circular conductor. The algorithm can be implemented on a low-cost MCU for automatic real-time operation. Unlike other coreless magnetic field sensors that need to be fixed onto the conductor for accurate current measurement, the proposed sensor unit affords a more flexible installation option. A hardware prototype is constructed for the proposed coreless current sensor unit. The performance evaluation results show that the accuracy of the proposed sensor unit is comparable to the conventional magnetic core CTs.