• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.589-591
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• 2008

본 논문은 연자성체(Iron powerder)인 일명 SMC(Soft Magnetic Composite)를 적용한 3상 BLDC motor의 설계 및 제작, 측정에 관한 연구이다. 특히 본 연구에서는 냉장고 압축기용 120W급 3상 BLDC motor에 관한 것으로써 연자성체를 적용시 모터 특성결과에 대하여 기술하였다. 아울러 SMC를 이용한 모터설계의 기준을 제시하였다. SMC 재질은 일반 실리콘 강판에 비해 코어의 3차원 형상을 자유롭게 제작 할 수 있으며, 고속 회전시 발생하는 철손을 감소시킬 수 있어 모터 코어용으로 많은 연구가 이뤄지고 있다. 따라서 본 논문에서는 우선 2차원 설계를 통하여 냉장고 압축기용 BLDC motor의 코어를 SMC 재질로 제작 성능 측정 하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.5
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• pp.457-462
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• 2014

Given their low cost, single rolling piston compressors (SRPC) are utilized in low-power room air-conditioning systems. The SRPC cycle is composed of one compression and discharge process per mechanical rotation. The load torque is high during the compression process of the refrigerants and low during the discharge process of the refrigerants. This load torque variation induces a speed ripple and severe vibration, which cause fatigue failures in the pipes and compressor parts, particularly under low-speed conditions. To reduce the vibration, the compressor usually operates at a high-speed range, where the rotor and piston inertia reduce the vibration. At a low speed, a predefined feed-forward load torque compensator is used to minimize the speed ripple and vibration. However, given that the load torque varies with temperature, pressure, and speed, a predefined load torque table based on one operating condition is not appropriate. This study proposes an online load torque compensator for SRPC. The proposed method utilizes the speed ripple as a load torque ripple factor. The speed ripple is transformed into a frequency domain and compensates each frequency harmonic term in an independent feed-forward manner. Experimental results are presented to verify the proposed method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.39-46
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• 1994

Experiments on the performance of refrigeration system using alternatives to R12 are carried out. The condenser and the evaporator are concentric-tube heat exchangers of counter-flow type and the compressor is driven by a variable speed motor. In this study, R134a, R152a, R22/142b(50 : 50 by mass) are adopted as alternatives to R12. Tests are performed by varying the inlet and outlet temperatures of secondary fluids of evaporator and condenser under the condition of constant compressor speed, degree of superheating and degree of subcooling. Results show that R134a has refrigeration capacity close to that of R12 and requires the greatest compressor power compared with that of others. And the system using R152a shows the best performance from the viewpoint of refrigeration capacity, compressor power and coefficient of performance. R22/142b is superior to R12 in the above points.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.51-56
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• 2015

Cryogenic cooling system for HTS electric power devices requires a reliable and efficient high-capacity cryocooler. A Striling cryocooler with a linear compressor can be a good candidate. It has advantages of low vibration and long maintenance cycle compared with a kinematic-driven Stirling cryocooler. In this study, we developed dual-opposed linear compressor of 12 kW electric input power with two 6 kW linear motors. Electrical performance of fabricated linear compressor is verified by experimental measurement of thrust constant. The developed Stirling cryocooler has gamma-type configuration. Piston and displacer are supported with flexure spring. A slit-type heat exchanger is adopted for cold and warm-end, and the generated heat is rejected by cooling water. In cooling performance test, waveforms of voltage, current, displacement and pressure are obtained and their amplitude and phase difference are analysed. Moreover, temperatures of cooling water, housing and linear motor are recorded and electric power parameters of driving circuit are also obtained. The developed Stirling cryocooler reaches to 47.8 K within 23.4 min. with no-load. From heat load tests, it shows cooling capacity of 440 W at 78.1 K with 6.45 kW of electric input power and 19.4 of % Carnot COP.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.33-42
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• 1997

The reciprocating compressors are widely used in industrial fields for its simplicity in principle and high efficiency. But the design of it requires rigorous experiments due to its high dependence on many design parameters. In this work, a mathematical model is developed so that we can analyze the gas-solid interaction during the whole working processes of a reciprocating compressor. The governing equations, which represent the fluid-solid interaction, was derived from the unsteady Bernoulli's equation with the assumption of quasi-steady working process. The valve itself was assumed to be a one degree of freedom spring-mass-damper system. A simple thermodynamic relation, the ideal gas state equation, was used to give it an external force term assuming that the refrigerant behaves like an ideal gas. It was suggested to use a motor of higher driving frequency to enhance the performance of the reciprocating compressor without causing a faster failure of the valve.

• 연구논문집
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• s.33
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• pp.39-51
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• 2003

This paper deals with the noise measurement and evaluation method of a reciprocating air-compressor and its noise reduction. Lead-wrapping techniques are employed to identify the contribution of principal noise sources which are generally known as motor, belts, suction/discharge valves, moving piston, and flow-induced noise which are caused by edges or discontinuities along the flow path e.g. expansions, contractions, junctions and bends. As a result, it can be found that main noise sources of the air-compressor can be categorized by the suction/discharge noise, valve noise, and compressed-air tank noise. Based on the investigations, mufflers are designed to reduce both the suction/discharge noise and the compressed-air tank noise. Instead of the conventional valve plate, engineering plastics are used as a new one for the reduction of valve impact noise. In addition, attempts are made to reduce the valve noise propagation to the cylinder head and the compressor tank by using the insulation casings in the cylinder head. As a result of the countermeasure plans, it can be achieved that the noise reduction of the air-compress is up to 10 dB.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.1
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• pp.33-47
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• 1992

Experimental investigation on the performance of a heat pump system using refrigerant mixtures is done. The condenser and the evaporator are double pipe heat exchangers of counter flow type and the compressor is driven by a variable speed motor. The refrigerant mixture used in the experiment is R22/R142b. Experiments are performed by changing the compressor speed, composition on ratio of mixture, and the average temperatures of condenser and evaporator. The compressor work, heating capacity and the coefficient of performance are calculated. Results show that the heating capacity can be changed by varying the mass flow rate of refrigerant mixtures to meet the heating load. It is shown that the capacity control by changing the composition ratio is more effective than by changing the compressor speed. Under the condition where the external conditions are fixed and the heating loads are equal, the coefficient of performance has its maximum value near 50 : 50 mass fraction of the refrigerant mixture in this study.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.95-95
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• 2013

The NdFeB magnet can be classified into the sintered magnet and bonded magnet. The former has superior magnet characteristics but the degree of freedom in shape is highly restricted, whereas the latter has a high degree of freedom, but its magnet characteristics are inferior to the former. When a NdFeB magnet is used at the elevated temperature, part of Nd must be replaced with a high priced Dy to increase its coercive force. For these reasons, a Dy free and high performance NdFeB bonded magnet is desired strongly. The author successfully developed a Dy free NdFeB anisotropic bonded magnet based on discovery of new phenomena called as d-HDDR reaction and its mass production process such as a thermally balanced hydrogen reaction furnace, micro capsuled powder, compression molding / injection molding under magnetic field, magnetic die and so on. Applied to DC brush seat motor for automotive use, the motor has become 50% small in size and weight. The commercialization of a half sized motor for automotive use has been realized up to the market share of 30%. At present, its commercialization is extending to various types of motors such as power tool, ABS motor, wiper motor, window motor, electric bike power motor, and compressor motor. It is expected that the applications will be increasingly enlarged to EV motor, wind generator, EPS motor, washing machine, and glass cutting machine. This innovative technology has realized Dy free high performance magnet and mudt make big contribution to not only rare element strategies but also energy conservation.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.173.1-173.1
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• 2011

The high fuel flexibility of gas turbine power system has boosted their use in a wide variety of applications. Recently, the demand for biogas generated from the digestion of organic wastes and sewage waste water as a fuel for gas turbines has increased. We investigated the performance of high pressure biogas compression system and operating conditions for supplying biogas. The total flow per minute of biogas from food waste water digestion tank is $54Nm^3$. The main type of biogas compression system is the reciprocating system and screw type system. The target of biogas mechanical data is the as belows; inlet pressure 0.045bar, supplying biogas temperature is $30{\sim}60^{\circ}C$, and final pressure is above the 25 bar. Also, inlet conditions of biogas consist of CH4 48.5%~83%, $H_2S$ Max. 500ppm, $NH_3$ Max. 1,500ppm and Siloxane 2.7~4.6ppm. The boosting Blower system raises a pressure from 0.045bar to 1bar before main compressor. The main system lay out of reciprocating consisits of compressor driver, filter, cooling system, blowdown vessel, control system and ESD(Emergency Shut Down) system. And an enclosure package needs to be installed for reducing noise up to 75dB. The system driver is the electronic motor of explosion proof type. Forthe compressor system reliable operation, the cleaning system something like particulate filter needs to be set up in the inlet of compressor and Coalescing Filter in the outlet of compressor. Particulate Filter has to be removed above $10{\mu}m$ size of the particles in biogas. The coalescing filter(Micofine Borosilicate Glass Fibers Filter treated phenol acid) also removes moisture and oil of above $0.3{\mu}m$ to be involved in high pressure biogas up to 90%~98%.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.91-96
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• 2013

Recently, it is increased to apply sensorless drive for BLDC (Brushless DC) motor to household electrical appliances, especially in the refrigerators and air conditioners, to reduce the cost and the acoustic noise by the operation and to make their functions more comfortable for human beings. In this paper, low-cost sensorless drive for BLDC motor is implemented by random PWM (Pulse Width Modulation). The experimental results show that the electromagnetic noise was reduced and the sound quality was improved by BLDC motor sensorless random PWM Control.