• Journal of Power Electronics
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• v.10 no.1
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• pp.58-64
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• 2010

In this paper, the dynamic performance of oscillating linear motors, which are used in household refrigerators, is improved by means of efficient parameter identification. Oscillating linear motor parameters are identified as a function of the piston position and the motor current. They are stored in a ROM table and used later for an accurate estimation of piston position. The identified motor parameters are also approximated to the $2^{nd}$-order surface functions, which are divided into 2 or 4 subsections in order to decrease identification errors. Experimental results are given to show that the proposed control scheme can provide oscillating linear motors with high dynamic performance.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1219-1226
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• 2017

This paper presents the hybrid stepping machine for linear oscillating generators. The focus of the work is the suggestion of the improved model through the comparison of proposed models ; new flux concentrating PMs mover of the hybrid stepping generator is proposed based on the symmetrical and non-symmetrical stator cores of the surface mounted PMs mover, and non-slanted PMs and slanted PMs of the flux concentrating PMs mover. It is achieved using equivalent magnetic circuit considering leakage elements. Finally, this study suggests new hybrid stepping structure of linear oscillating generator.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.756-758
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• 2003

In the machine tool industry, direct drive linear motor technology is of increasing interest as a means to achieve high acceleration, and to increase reliability. This paper deals with the characteristics of tubular type linear oscillating actuator with Halbach magnet array. The magnetic field solutions are derived analytically in terms of vector potential, two dimensional cylindrical coordinate system and Maxwell's equations. Motor thrust, flux linkage, back emf are then derived. The results are shown in good conformity with those obtained from the commonly used finite element method. Test results such as thrust measurements are also given to confirm the analysis.

• Journal of Power System Engineering
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• v.21 no.5
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• pp.5-12
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• 2017

With the difficulties in increasing the efficiency of conventional crank-driven compressors due to mechanical loss, compressor manufacturers have investigated new kinds of compressor such as a free piston compressor mechanism. This study investigates the energy efficiency of two different types of compressor for a household refrigerator. One is the conventional crank-driven compressor, and the other one is a linear compressor. The energy efficiencies of these compressors are evaluated. Experimental results show that the linear compressor has 10% lower power consumption than the brushless direct-current (BLDC) reciprocating compressor. The linear compressor demonstrates excellent energy efficiency by reducing the friction loss. Furthermore, a motor efficiency exceeding 90% is achieved by using a linear oscillating mechanism with a moving magnet. Additionally, the compressor stroke to piston diameter ratio of the oscillating piston in the linear compressor can be adjusted in order to modulate the cooling capacity of the compressor for improved system efficiency.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1048-1050
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• 2003

Recently, many linear motion generators and motors are rapidly finding applications that ranges from short stroke linear motion vibrators, such as dynamic con type loud speakers to stilting engine driven linear reciprocating alternators, compressors, textile machines etc. In this paper, we analyze the characteristics of tubular linear motor with Halbach and radial magnet array respectively. We already derived magnetic field solutions due to the PMs and to the currents and Motor thrust. On the basis of analytical field solutions, this paper deals with flux linkages and back emf. The results are validated extensively by comparison with finite element analyses. Then, this parer also presents thrust characteristics according to design parameters for each model.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.43-47
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• 2012

A linear compressor generates pulsating pressure and oscillating flow in a cryocooler such as Stirling cryocooler and pulse tube refrigerator. It is driven by AC power source and designed to operate at resonance of piston motion. The driving voltage level is determined by electric parameters of resistance, inductance and thrust constant of linear motor. From voltage equation on linear motor, the power factor of driving power is inherently less than 1. The phase difference between voltage and current of supplied power can be zero using capacitor and this can minimize a supply voltage level. Especially, the linear compressor of kW class requires high voltage and thus can cause a difficulty in selecting power supply unit due to limitation of voltage level. The capacitor in driving electric circuit is useful to settle this problem. In this study, the electric circuit of linear compressor is analytically investigated with assumption of mechanical resonance. The electric parameters of commercial linear motor are used in the analysis. The effects of capacitor on driving voltage level and power factor are investigated. From analytic results, it is shown that the voltage level can be mimized with using capacitor in driving electric circuit.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.697-702
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• 2004

LG Electronics developed linear compressors for a household refrigerator which can reduce energy consumption up to $24\%$ by only Drop-ln instead of a conventional reciprocating compressor. The linear compressor is composed of a linear oscillating motor, a piston directly coupled with the linear motor, a cylinder and the specific discharge system of LG. Because of this free-piston structure, the position of the piston can be changeable according to the voltage variation, load variation and so on. By this reason, LG linear compressor has been in need of an additional unit to control the position of the free-piston stably. In this paper we will introduce the innovative technology which is able to operate the linear compressor without controlling the piston position like a conventional reciprocating compressor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.537-544
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• 2015

This paper provided two types of design method on moving core type LOA and one type of design method on moving coil type LOA, and compared and examined each of its characteristics. In order to conduct parametric design process, voltage equation was used to schematize Lmin/K and L/M map, and the schematized map was used to determine Lmin, K or L, M. In order to meet requirements such as thrust force and input voltage and to satisfy the target values of Lmin, K or L, M, the types and sizes of each type were designed using geometry design process. 2-FEA was conducted for each of the designed model. After examining thrust force based on the location of the mover, Type-1 showed radical change in thrust force as movers moved, and Type-2 and Type-3 showed constant appearance of thrust force. The total volume of the designed LOA model was compared to select the model with highest thrust force density. Also, the weight of the mover for each model was compared in order to select the model that was predicted to have highest mechanical responsiveness and stroke characteristics.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.15-18
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• 1996

In the case of need for reciprocating motion, the study for application of Linear Oscillating Actuator(LOA) is being accomplished. LOA is the simpler and more efficient than other linear apparatus using the rotary motor because LOA produce the thrust force without any converter such as cam, clutch, rack, pinion and belt, etc. We designed the flat moving core type LOA and manufactured for trial. This paper shows the structure and dynamic characteristics of LOA.

• Tribology and Lubricants
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• v.26 no.6
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• pp.311-316
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• 2010

Surface texturing of micro dimple or pore-shaped pattern was prepared using a fiber laser system. Surface texturing was designed to have a square pattern with a particular pitch distance for each corresponding density of 5, 10, 20, and 30%. Thermal damages such as bulges and burrs formed during laser irradiation were observed around the dimples. Thermal damages were later removed by lapping using alumina particles of $0.3{\mu}m$ in diameter. Oscillating friction tests were performed against heat-treated high speed steels under lubricated condition. The lubricant used was SAE 5W-30 automotive engine oil. Normal contact pressure and oscillating frequency was 0.28 MPa and 20 Hz, respectively. The tests were continued for 20 minutes, and friction plots were recorded for examination. Results revealed that the coefficient of friction was lowered regardless of texturing density. Moreover, the lowest coefficient of friction was obtained for 10% density texturing. It is attributed to increased lubricity due to the introduction of surface texturing. In addition, it is concluded that the optimum texturing density and pattern must be found for the best lubricity and low friction.