Contactless Current Sensors Based on Magnetic Tunnel Junction for Smart Grid Applications

Abstract

Advanced sensing techniques are key technologies required for the smart grid. Magnetic tunnel junction (MTJ) sensors hold great promises in the distributed linear current sensing, with small size, low price, and excellent performances. In this paper, MTJ Wheatstone bridge sensors were fabricated, attaining a typical sensitivity of 4.94 mV/V/Oe with an offset of −2.84 mV/V. A contactless current sensor based on the MTJ sensor was designed and realized, achieving a sensitivity of 7.75 mV/A and an offset of −8.68 mV. We can adjust the sensitivity and the linear range of the sensor by changing the gap of the magnetic core, and make the sensor much less susceptible to electrical wire’s location and orientation. This paper provides a practical current sensing technique for smart grid applications.