• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.91-98
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• 2012

Climate change and other pollutions make a huge demand of environment friendly and high efficient motors especially Brushless DC (BLDC) motors. Generally, bidirectional energized BLDC motors are used widely; however, inverter devices used in the driver put fear of being effected by noise. This paper proposes unidirectional energized BLDC motor which utilizes asymmetrical H-bridge circuit as the driver circuit. The Minato motor is one of the pioneers in unidirectional energized system. The use of bar magnets in the rotor is one of the biggest disadvantages of the motor. We proposed using tabular magnets. The paper compares the power consumption and efficiency of the Minato motor and the proposed motor. During high speed rotation, undesirable armature current is generated that has a deceleration characteristic. This current lowers the motor's efficiency. In this paper, we propose the solutions and show comparison through equations of the copper loss ratio for the Minato and our proposed motors. The third motor, which has the highest efficiency, was discovered during examination of the equations.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.2
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• pp.18-22
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• 2012

This paper presents a method and the experimental measurement system for the determination of Jiles-Atherton model parameters of the 30ZH120 electrical steel sheet. The paper utilizes Epstein Square devices to proceed with the experiment and measurement on a group of hysteresis loops of some certain transformers which use the 30ZH120 electrical steel sheet under two different lap ways. The approach relies on the simulated annealing optimization method in order to minimize the error between the measured and modeled hysteresis curves and yield the best five Jiles-Atherton model parameters. A convenient program, based on the Simulink platform, that can identify the J-A model parameters automatically from the experimental saturated hysteresis loop which is used to model the nonlinear characteristics of the electrical steel sheet, is developed. Research shows that the simulated annealing optimization method gets satisfactory results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.123-124
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• 2006

Usually, hydraulic cylinder is widely used as the actuator in the equipment of construction machines, airplane and military machines. In case of these devices, due to use under severe environment such as water, $SiO^2$ and dust, etc. seal which has high packing ability and long service life has been required. These characteristics are largely influenced by material and geometries of seal such as approach angle, withdrawal angle and interference. Recently, many a study about seal material has been performed so that many materials have been developed. But the concrete studies including the relationships between geometry of seal and sealing performance have hardly been performed yet. Therefore, in this study, we predicted the deformation behavior and contact normal distribution of dust seal with the variation of geometries of seal lip using finite element analysis. And based on the results of analyses, we discussed the effects of the design variables fur sealing performance of the dust seal.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.822-824
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• 2000

To apply HTS to AC devices, it is necessary that study theoretically and experimentally to analyze the AC losses. It should be investigated the theoretical mechanisms precede the actual experiments. Because the AC losses cause some complicated troubles in AC machines, we can design the machines properly. In this study, firstly we analyze the basic cause of AC losses by investigating the several loss factors, secondly measure the AC losses of HTS by using Magnetization. Technique and this results show that AC losses of HTS is tenuous than those of general materials used in power system. Consequently we can compare the actual results with the theoretical results. And we find that AC losses of HTS are related to the amplitude of external magnetic field and the frequency. Through this study, we find that it is possible to apply the results by Magnetization. Technique to the AC power system, to the design of AC machine, to design of HTS proper to the foretold AC losses.

• The KIPS Transactions:PartA
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• v.12A no.3 s.93
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• pp.229-234
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• 2005

The virtual machine is a programming environment that supports device and platform independence. So far, virtual machines such as JVM and KVM have been used in a variety of environments for the Java language. Some virtual machines similar to them are also being developed and used. This paper Presents the experiences of extracting elements essential for small sized devices such as PDA from Java Class files(*.class) and designing a converted class file(*.rclass) for runtime efficiency by modifying its class file format and developing its translator. In addition, a virtual machine is developed to receive the translated class file entered and output the runtime results.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.372-378
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• 2012

This paper deals with a 3-phase voltage disturbance generator for a performance test of custom power devices such as dynamic voltage restorers (DVR), dynamic uninterruptable power supplies (UPS), etc. The operating principle of the proposed circuit is described in each mode of voltage sag, swell, outage, and unbalance. The main components of the proposed disturbance generator are silicone controlled rectifier (SCR) thyristors, variable autotransformers, and transformers. Therefore, the disturbance generator can be implemented with a considerably low cost compared to the conventional pulse width modified (PWM) inverter and converter type generators. Furthermore, it has good features of high reliability with simple structure, high efficiency caused by no PWM switching of the SCR thyristors, and easy control with a wide variation range. To verify the validity of the proposed scheme, simulations and experiments are carried out.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.15.2-15.2
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• 2009

Manufacturing of printed electronics using printing technology has begun to get into the hot issue in many ways due to the low cost effectiveness to existing semi-conductor process. This technology with both low cost and high productivity, can be applied in the production of organic thin film transistor (OTFT), solar cell, radio frequency identification (RFID) tag, printed battery, E-paper, touch screen panel, black matrix for liquid crystal display (LCD), flexible display, and so forth. The emerging technology to manufacture the products in mass production is roll-to-roll printing technology which is a manufacturing method by printings of multi-layered patterns composed of semi-conductive, dielectric and conductive layers. In contrary to the conventional printing machines in which printing precision is about $50~100{\mu}m$, the printing machines for printed electronics should have a precision under $30{\mu}m$. In general, in order to implement printed electronics, narrow width and gap printing, register of multi-layer printing by several printing units, and printing accuracy of under $30{\mu}m$ are all required. We developed the roll-to-roll printing equipment used for printed electronics, which is composed of un-winder, re-winder, tension measurement system, feeding units, dancer systems, guide unit, printing unit, vision system, dryer units, and various auxiliary devices. The equipment is designed based on cantilever type in which all rollers except printing ones have cantilever types, which could give more accurate machine precision as well as convenience for changing rollers and observing the process.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.3
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• pp.40-46
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• 2009

Toroidally-wound brushless direct-current (BLOC) machines are compact, highly efficient, and can work across a large magnetic gap. For these reasons, they have been used in pumps, flywheel energy storage systems and left ventricular assist devices among others. The common feature of these systems is a spinning rotor supported by a set of (either mechanical or magnetic) bearings. From the view point of dynamics, it is desirable to increase the first critical speed of the rotor so that it can run at a higher operating speed. The first critical speed of the rotor is determined by the radial stiffnesses of the bearings and the rotor mass. The motor also affects the first critical speed if the rotor is displaced from the rotating center. In this paper, we analytically derive the flux density distribution in a toroidally-wound BLOC machine and also derive the negative stiffness of the motor, based on the assumption that the rotor displacement perturbs the flux density distribution linearly. The estimated negative stiffness is validated by finite element analyses.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.667-675
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• 2000

Force measuring devices should be calibrated to guarantee their test results. In order to establish the force standards in Korea, deadweight machines of 5 kN, 20 kN, 100 kN and 500 kN capacity and a hydraulic force standard machine of 2 MN capacity were installed at the Korea Research Institute of Standards and Science(KRISS). As heavy industries in Korea have been developed, we should measure large forces over 2 MN capacity precisely in industries. We developed a 10 MN force standard machine with built-in force transducers which is more compact and cheaper than hydraulic force standard machines which have been widely used as large force standards in most national metrology laboratories. Test results reveal that the relative expanded uncertainty of the force machine is less than 4.1 $\times$ 10-4 in the range of 1 MN-4.5 MN.

• Journal of Convergence for Information Technology
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• v.9 no.5
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• pp.34-39
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• 2019

One of the words frequently mentioned in our society today is the smart machine. Smart machines are machines that contain smart or intelligent functions. These smart machines have recently been applied in our home environment. These are phenomena that occur as a result of smart home. In a smart home environment, smart speakers have moved away from traditional music playback functions and are now increasingly serving as interfaces to control devices, the various components of a smart home. In this study, the technology trends of domestic and foreign smart speaker market are examined, problems of current products are analyzed, and necessary core technologies are described. In the domestic smart speaker market, SKT and KT are leading the related industries, while major IT companies such as Amazon, Google and Apple are focusing on launching related products and technology development.