A Novel Current Sensor Using FeCuNbSiB Single Nanocrystalline Toroidal Core and Double-Winding Excited by Multivibrator

Abstract

Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">73.5</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13.5</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sub> , nanocrystalline toroidal magnetic core made by furnace annealing at 823 K under nitrogen atmosphere shows good thermal stability of magnetic properties and excellent soft magnetic properties due to the greatly released internal stresses of the core during the isothermal annealing relaxation process. Based on the characteristic of the sensitive magnetic core, we proposed a novel non-contact type current sensor, which adopted single nanocrystalline core and double-winding excited by multivibrator bridge circuit. The sensor shows leading features that the sensitivity is inversely proportional to the number of turns of the winding and the sensitivity is nearly not related to the voltage supply provided for the bridge when some conditions are satisfied. The measuring principle was given in more detail by building ideal hysteresis loop model for the magnetic core. The observed experimental phenomenon is well consistent with the theoretical results and the theory indicates clearly the key factors affecting the performance parameters of the sensor, such as the coercive force,H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , and the magnetic flux of the sensing materials, the number of turns of the coils and circuit parameters, such as the values of resistors, capacitors and the transistor parameters, V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</sub> ,V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">be</sub> ,in the multivibrator bridge. In other words, we can design sensor freely to meet some requirements according to the given theory. The output signal of the multivibrator bridge was analysed by Fourier transform. Moreover, according to the theoretical results, the method to design the corresponding signal conditioning circuit was presented. The linear range of the sensor can be adjusted from 200 mA to 8 A with nonlinearity less than 0.5%F.S.