Residual magnetization measurements of a motor to be used in satellites

Abstract

A simple magnetic shielding system for residual magnetization measurements of a motor to be used in satellites is studied. The system consists of same-sized square coils, namely three sets of Simple Cubic-3 coil system. Because the system can generate a uniform magnetic field, we investigate the uniformity of the site. With a first-order gradient coil, the geomagnetic field can be reduced to less than 100 nT in a relatively large area. Inside of the system, the residual magnetization measurements of a step motor are demonstrated. An approach to reduce the magnetic field leakage from the step motor is also presented.Keywords： Geomagnetic field canceling, step motor, magnetic moment, square coil system 1．Instructions:Satellites are supposed to be able to control their positioning and stability in space. Therefore, the equipment installed in the satellite should be measured for residual magnetization during prelaunch [1]. In order to measure residual magnetization, the Japan aerospace exploration agency (JAXA), for example, has a ferromagnetic shield with triple spherical permalloy shells [2]. Although the shielding factor is as large as 60 dB for dc fields, typical magnetic fields inside a device are 20~40 nT. The usable area is limited because of the magnetization of the inner shell. Instead of a heavy ferromagnetic shielding system, the space research facilities are considering a geomagnetic field canceling system that uses the magnetic field generation coil [3]. A geomagnetic field canceling system requires uniform magnetic field generation over a considerable volume. From the point of view of practical advantages construction and usefulness, several kinds of square coil system have already been proposed. While the number of square coils allows the axial field to have good uniformity in a large volume, the size of the entrance area is limited by coil crossing for the three orthogonal coils sets. In order to drive one power supply in one direction, the ratio of the current in the coils should be an integer, and it is relatively tolerant of small design imperfections. For the reasons mentioned above, we have proposed a Simple Cubic-3 (SC3) coil system [4]. It consists of three square coils, with same coils' distance and a simple integer ampere-turn ratio.This paper presents the results of residual magnetization measurements of a motor to be used in satellites with our proposed geomagnetic field canceling system. We chose a suitable site through the measurements of geomagnetic fields at several locations, and constructed a system with three sets of SC3. Combined with a gradient field generation coil system (G2), the geomagnetic field can be reduced to less than 100 nT in a relatively large area. Inside of the system, we demonstrate the residual magnetization measurements of a step motor. An approach to reduce residual magnetization is also presented. Geomagnetic field canceling system: Geomagnetic field measurementIn order to choose a suitable site for the system, we investigated the uniformity of a magnet...

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Consideration of Array Module Design for Energy Harvesting of Power-Line Magnetic Noise

“…The side length was 2 m and the number of windings was 24:12:24. In the area within a radius of 50 cm from the center, SC3 can generate a uniform magnetic field to within ± 1 % deviation [10]. Because the maximum diameter of the modules was 20 cm, we used this area to simulate power line magnetic noise.…”

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“…2 shows the schematic design of the experimental setup used to measure the shielding factor. For the measurement, we used Simple-Cubic-3 coil system (SC3) we developed [1]. The three sets of SC3 can generate a uniform magnetic field in three-dimensions.…”

“…The coil system is an extremely effective method of magnetic shielding for a uniform external magnetic field. For example, we evaluated the leakage magnetic field from a motor to be used in satellites after reducing the geomagnetism in laboratory environment less than 100 nT [1]. The magnetic shielding using magnetic materials is a method of forming a space reduced magnetic field by leading the external magnetic field to the magnetic layer.…”

“…The authors have been developing magnetic shielding systems using a coil system for producing a uniform magnetic field or magnetic materials [1][2][3]. The coil system is an extremely effective method of magnetic shielding for a uniform external magnetic field.…”