Developing MEMS electric current sensors for end-use monitoring of power supply: Part VII - magnetic field distribution surrounding three-phase four-wire appliances under symmetrical loads

In this work, a passive and non-contact current detection method for three-phase four-wire appliances under symmetrical loads is proposed for the first time. The sensor consists of a piezoelectric cantilever with a permanent magnet mounted to its free end. When placed near appliances carrying AC currents, the magnet couples to the oscillating magnetic field around appliances, deflecting the cantilever and generating a sinusoidal voltage proportional to currents. In order to achieve a higher measurement sensitivity, the optimal location for magnet is determined by preliminary theoretical analysis and simulation method. The proposed low-power and non-invasive method, useful in real-time health monitoring of electrical equipment like three-phase motors, three-phase transformers and other related ones, is also applicable to future industry WSN.