• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.28-31
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• 2015

Electromotive forces (EMF) are generated by electrical equipment and engine shafting with a number of reasons. The shaft and bearing which is insulated by lubricating oil acts as a condenser, being able to store this EMFs. The electromotive force on the hull and shaft, with very few exceptions, has anode voltage on it. Electrical spark of the anode voltage on the shaft may lead to corrosion. Hence, in order to prevent ship's shaft and propeller corrosion, shaft grounding system are installed and operated. The shaft EMF voltage measurement methods was measured using 24bit 2 channels A/D converter of NI company and Labview software. 1 channel was propeller shaft's voltage and the other was M/E engine rpm gauge. In this paper, the generated electromotive force was analyzed and modeled with result of the analysis. As a result, the main shaft's electromotive force was in direct proportion to the main engine's revolution. However, over the specific R.P.M., it was reduced gradually. In addition, higher electromotive force on the shaft was identified during engine's ahead direction than the astern direction. The generated electromotive force is only minor compared to the shaft grounding system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.135-140
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• 2022

Most machines are made of several types of . In particular, the shaft system of the ship consists of the brass of the propeller blade and the stainless steel of the shaft. When dissimilar the electrolyte solution of seawater, a voltaic cell and a shaft electromotive force is generated. This electromotive force causes electrical corrosion of the bearing and shaft supporting the shaft system. prevent this corrosion, a shaft grounding system is installed in ships. As for the experimental method, various information acquired by designing a program to periodically measure the electromotive force of the controllable pitchpropeller) system using an A/D converter of NI. This study analyzed the generation and characteristics of accumulator electromotive force for CPP and considered the installation location of the grounding system to remove the accumulator electromotive force.

• Journal of Welding and Joining
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• v.33 no.4
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• pp.57-62
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• 2015

Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing(ECT) is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. The New ECT sensor which can detect inner defects was developed regardless the condition of surface. This sensor is verified to do experiment which measure the loss of induced electromotive force. The loss of induced electromotive force was measured in 5.4% and this low frequency ECT device can detect internal defects at depth 20 mm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.627-628
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• 2013

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.32-34
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• 1997

For a given brushless DC linear motor, we suggest the numerical prediction methods to analyze it's thrust characteristics. First, we calculate the magnetic flux density by the finite element method, and we then compute the maximum thrust with three computational methods - a Lorentz equation, a Maxwell stress method and a virtual work method. To confirm the accuracy of the computational methods, we measure the thrust of the linear motor made by our laboratory with a force-torque sensor. Also, we calculate the thrust by the measured back electromotive force. To choose the appropriate method for a specified application, we compare the maximum thrusts of the computational method and the calculation by the back electromotive force with the measured one. We conclude that the Maxwell stress method is turned out the best because it has the most accurate results among three computational methods and it is more convenient than the calculation method by the back electromotive force.

• Journal of Magnetics
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• v.20 no.3
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• pp.252-257
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• 2015

This paper investigates the concept and implementation of an energy harvesting device using a ferrofluid sloshing movement to generate an electromotive force (EMF). Ferrofluids are often applied to energy harvesting devices because they have both magnetic properties and fluidity, and they behave similarly to a soft ferromagnetic substance. In addition, a ferrofluid can change its shape freely and generate an EMF from small vibrations. The existing energy harvesting techniques, for example those using piezoelectric and thermoelectric devices, generate minimal electric power, as low as a few micro-watts. Through flow analysis of ferrofluids and examination of the magnetic circuit characteristics of the resultant electromagnetic system, an energy harvester model based on an electromagnetic field generated by a ferrofluid is developed and proposed. The feasibility of the proposed scheme is demonstrated and its EMF characteristics are discussed based on experimental data.

• Transactions of the Society of Information Storage Systems
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• v.2 no.2
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• pp.117-122
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• 2006

A novel method to find interaction dynamics between focusing direction and tracking direction in an optical pick-up is proposed. and the decoupling control to reduce the interaction effect is discussed. First, the basic principle to detect dynamic interaction analysis using back electromotive force is introduced. Second, the interaction analysis between focusing and tracking direction of is analyzed for a commercial slim type optical pick-up. Finally. decoupling control process and its simulation results are shown.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.97-102
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• 2017

A current transformer (CT) is a type of sensor that consists of a combination of electric and magnetic circuits, and it measures large ac currents. When a large amount of current flows into the primary winding, the alternating magnetic flux in the iron core induces an electromotive force in the secondary winding. The characteristics of a CT are determined by the iron core design because the iron core is saturated above a certain magnetic flux density. In particular, when a large current, such as a current surge, is input into a CT, the iron core becomes saturated and the induced electromotive force in the secondary winding fluctuates severely. Under these conditions, the CT no longer functions as a sensor. In this study, the characteristics of the secondary winding were investigated using the time-difference finite element method when a current surge was provided as an input. The CT was modeled as a two-dimensional analysis object using constraints, and the saturation characteristics of the iron core were evaluated using the Newton-Rhapson method. The results of the calculation were compared with the experimental data. The results of this study will prove useful in the designs of the iron core and the windings of CTs.

• Smart Structures and Systems
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• v.22 no.2
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• pp.139-150
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• 2018

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to expand the operational range of a regular generator through a simple and robust active control strategy. It has a broad range of applications in hybrid vehicles, wind turbines, water turbines, and similar technologies. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with an active control system, which adjusts the overlap ratio based on the desired output power at different rotor speeds for a specific application, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator results in reduced torque loss of the generator and an increased rotational speed of the generator rotor. A VEG can improve the fuel efficiency of hybrid vehicles; it can also expand operational ranges of wind turbines and water turbines and harness more power.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1403-1413
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• 1996