Derac Son

Development of Micro-size Search Coil Magnetometer for Magnetic Field Distribution Measurement

For the measurement of the magnetic field distribution with high spatial resolution and high accuracy, the magnetic field sensing probe must be non-magnetic, but the MFM probe and sub-millimeter-meter size Hall probe use a ferromagnetic tip and block, respectively, to increase the sensitivity. To overcome this drawback, we developed a micro-size search coil magnetometer which consists of a single turn search coil, Terfenol-D actuator, scanning system, and control software. To reduce the noise generated by the stray ac magnetic field of the actuator driving coil, we employed an even function λ-H magnetostriction curve and lock-in technique. Using the developed magnetometer, we were able to measure the magnetic field distribution with a magnetic field resolution of 1 mT and spatial resolution of 0.1 ㎜ × 0.2 ㎜ at a coil vibration frequency of 1.8 ㎑.

Magnetic Shielding Effectiveness Measurement of Magnetic Steel Sheets in ELF Range

In this study, a new kind of instrument for measuring the magnetic shielding effectiveness (MSE) was developed using a double yoke; one a magnetizing yoke and the other a sensing yoke. Using the developed instrument, the MSE could be measured for a steel sheet specimen in the ELF range, where the magnetic permeability contributes to the MSE at low frequencies and eddy currents contributes to the MSE high frequencies with ＜ 0.1 ㏈ reproducibility. The developed measuring method can be applied to quality control in a steel sheet company producing EMI/EMC shielding materials

Prediction of Core Loss Including Higher Harmonic Inductions Using Two Symmetrical AC Minor Loops

For the induction motor and inverter type motor design, prediction and analysis of core loss including higher harmonics have been studied. In this work, we have generated two symmetrical ac minor loop in the fundamental hysteresis loop whose positions are zero induction region and saturation induction region, and we could predict core loss including higher harmonics inductions. using the following modified superposition principle; Pc(B。, f。, Bh, nf。)=Pc(B。, f。)+(n-1)[k₁(B。)P_(cL)(Bh, nf。)+(1-k₁(B。))P_(cH)(Bh, nf。)]. Using this equation we could also analyze core losses including higher harmonic induction under different maximum magnetic induction, different amplitude of higher harmonic induction with different harmonic frequencies.

Major B-H Loop Measurement of Toroidal Shape Magnetic Powder Core

Dept. of Photonics and Sensors, Hannam University, Hannamro 70, Daedeok-gu Daejeon 306-791, Korea(Received 9 June 2014, Received in final form 18 June 2014, Accepted 19 June 2014)Toroidal cores made of metallic powder requires large magnetic field strength up to few decade kA/m to obtain major hysteresisloop. To overcome thermal heat generation problem from large exciting current during measurement, we have employed a real timehysteresis loop tracer which can digitize and calculate B-H signals in personal computer as real time. For example, when wemagnetize specimen at 10 Hz frequency, we could display hysteresis loops 10 times per second. Using the real time hysteresis looptracer, we could measure major hysteresis loop of toroidal shape metallic powder core at maximum flux density or maximummagnetic field strength to be measured within 5 second not to significant increasement of specimen temperature due to the heatdissipation from coil windings. For the constructed hysteresis loop tracer, we could measure hysteresis loop at magnetic field strengthhigher than 50 kA/m for the toroidal shape specimen.Keywords: magnetic measurement, toroidal core, magnetic powder core, B-H loop tracer, major hysteresis loop

Design and Fabrication of Digital 3-axis Magnetometer for Magnetic Signal from Warship

Dept. of Photonics and Sensors, Hannam University, Daejeon 306-791, Korea(Received 26 July 2014, Received in final form 18 August 2014, Accepted 18 August 2014)We developed a digital 3-axis flux-gate magnetometer for magnetic field signal measurement from warship during demagnetizingand degaussing processes. For the magnetometer design, we considered following points; the distance between magnetic fieldmeasurement station and magnetometer located under sea is about several 100 m, the magnetometer is exposed to magnetic field of± 1 mT during demagnetizing process, and magnetometer is located under the sea about 30 m depth. To overcome long distanceproblem, magnetometer could be operated on wide input supply voltage range of 16~36 V using DC/DC converter, and for the datacommunication between the magnetometer and measurement station a RS422 serial interface was employed. To improve permingeffect due to the ± 1 mT during demagnetizing process, magnetometer could be compensated external magnetic field up to ± 1 mT butmagnetic field measuring rang is only ± 100µT. The perming effect was about ± 2 nT under ± 1 mT external magnetic field. Themagnetometer was tested water vessel with air pressure up to 6 bar for the sea water pressure problems. Linearity of the magnetometerwas better than 0.01 % in the measuring range of ± 0.1 mT and noise level was 30 pT/ at 1 Hz.Keywords: Magnetometer, flux-gate magnetometer, low magnetic field, perming, amorphous core

Construction of Current Sensor Using Hall Sensor and Magnetic Core for the Electric and Hybrid Vehicle

A current sensor is one of important component which is used for the electrical current measurement during charge and discharge of the battery, and monitoring system of the motor controller in the electric and hybrid vehicle. In this study, we have developed an open loop type current sensor using GaAs Hall sensor and magnetic core has an air gap. The Hall sensor detect magnetic field produced by the current to be measured. The 3 mm air gap core was made by HGO electrical steel sheets after slitting, winding, annealing, molding, and cutting. Developed current sensor shows 0.03 % linearity within DC current range from -400 A to +400 A. Operating temperature range was extended to the range of using temperature compensating electronic circuit. To Improve frequency bandwidth limit due to the air flux of PCB (Printed Circuit Board) and Hall sensor, We employed an air flux compensating loop near Hall sensor or on PCB. Frequency bandwidth of the sensor was 100 kHz when we applied sine wave current of in the frequency range from 100 Hz to 100 kHz. For the dynamic response time measurement, 5 kHz square wave current of was applied to the sensor. Response time was calculated time reach to 90 % of saturation value and smaller than .

Interface between the Electroplated Copper-cobalt Thin Films and the Substrate

We electroplated copper-cobalt thin films on a silicon substrate, which had 150 nm thick copper seed layer. The adhesion between the two metallic layers could be increased by utilizing a proper organic additive, pulse plating technique, and high temperature annealing. The thin films exhibited columnar growth of the deposits and enhanced adhesion. This is attributed to the grain growth mechanism introduced by the additive and annealing.