Electrical Compensation for Magnetization Distortion of Magnetic Fluxgate Current Sensor

Abstract

Current sensors based on the fluxgate magnetic field meter and feedback zero-field operating principle have excellent current measurement accuracy and linearity in a large range of up to thousands of amperes. An excitation current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{e}$ </tex-math></inline-formula> ) is employed in a magnetic fluxgate sensor to magnetize the magnetic core periodically, which will generate magnetization distortion that affects the performance of the sensor. This article proposes a novel scheme for suppressing the magnetization distortion through electrical compensation. The source of the magnetization distortion is theoretically derived and analyzed. It is found that the magnetization distortion is a function of the excitation current <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{e}$ </tex-math></inline-formula> and is not affected by the primary current. Since <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{e}$ </tex-math></inline-formula> is a periodical current that is determined by the parameters of the sensor itself, it is feasible to inject a specified periodical current to the output port of the sensor to cancel the magnetization distortion. Compared with the magnetization distortion compensation method with an additional core and coil, this method does not need to pair the cores or coils, which significantly reduces the complexity of the production process and saves space for the sensor. A prototype sensor with electrical compensation is designed, fabricated, and tested. Experimental results show that the compensation setting significantly suppresses the magnetization distortion signal. The amplitude of the basic frequency component is reduced from 24 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.8 ~\mu \text{V}$ </tex-math></inline-formula> . The other odd harmonics of the magnetization distortion are also reduced. The electrical compensation method works properly in a large current range from −1.5 to 1.5 kA. The scale accuracy of the prototype sensor is less than 5.7 ppm (parts per million). The compensation method can suppress the magnetization distortion to a similar level with operating temperature changes from room temperature to 50 °C.