• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.44-50
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• 2006

A driver's feelings of transmission serve as a basis to judge not only the transmission but also the entire automobile that he or she drives. The importance of transmission feelings is increasing daily because of driver's desire for increased torque and other improved functions. In order to accommodate such desire of drivers, new friction materials have been developed. The study in this report compared the affects of such materials and the force for transmission theoretically and empirically. By doing so, the study attempted to establish basic references for computation of capacity and other factors to be determined at the time of design of synchronizer system.

• 전기의세계
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• v.22 no.2
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• pp.33-39
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• 1973

This paper presents numerical analysis by omputer for the steady state characteristics of the single phase reluctance motor driven by the bridge type SCR inverter and also the experiments were carried out to verify the numerical analysis data for the current, voltage, and torque of the motor. It shows that the inductance of the inverter, the capacity of the commutation condenser and the frequency of the inverter have great effects to the magnitude and wave form of the motor terminal voltage and current. It is clear that the capacity of the commutation condenser and the inductance of the inverter circuit have to be adequately selected in order to stabilize the motor operation.

• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.73-80
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• 2013

Purpose: This study was conducted to compare tillage and loads characteristics of three types of rotavators in farmland working condition of Korea. Methods: Tillage operations using three types of rotavators, i.e. rotary-type, crank-type and plow-type, were carried out in a dry field of Korea. The same prime mover tractor was used for driving three types of rotavators, and under several operational conditions, tillage characteristics such as actual working speed, rotavating depth, rotavating width, actual field capacity, flow of tilled soil, soil inversion ratio, and pulverizing ratio were measured. In addition, loads characteristics like torque and required power of Power Take-Off (PTO) shaft were calculated. Results: The average rotavating depth was smaller than the nominal value for all rotavators, and the difference was the greatest in the plow-type rotavator. Nevertheless, the plow-type rotavator showed the largest rotavating depth. The rotavating width was the same as the nominal value of all rotavators. The flow of tilled soil at the same operational conditions was the greatest in the plow-type rotavator and was the smallest in the rotary-type rotavator. In the most commonly used gear conditions of L2 and L3, the average soil pulverizing ratio was the greatest in the rotary-type rotavator, and followed by crank-type and plow-type rotavators in order. In the gear L2 and L3, the plow-type rotavator also had the lowest average soil inversion ratio while the rotary-type and crank-type rotavators had the same soil inversion ratio each other. The average torque and power of PTO shaft in the gear L2 and L3 were the highest in the plow-type rotavator. The load spectra of PTO shaft applying rain flow counting method and Smith-Waston-Topper equation to the measured torque showed that the modified torque amplitude was the greatest in the crank-type rotavator. This may come from the large torque fluctuation of crank-type rotavator during tillage operations. Conclusions: The three types of rotavators had different tillage and loads characteristics. The plow-type rotavator had the deepest rotavating depth, the smallest soil inversion ratio, the largest soil pulverizing ratio and required PTO power. Also, the crank-type rotavator showed a large torque fluctuation because of their unique operational mechanism. This study will help the farmers choose a suitable type of rotavator for effective tillage operations.

• Korean Journal of Agricultural Science
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• v.43 no.4
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• pp.656-664
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• 2016

Gear reducers are widely used for various agricultural machinery applications such as greenhouses, tractors, and agricultural vehicles. However, thermal deformation and surface pitting at gear tooth flank frequently occur in gear reducers due to high torque. Thus, surface heat treatment of gears is required to improve wear and fatigue resistance. The objective of this study was to simulate the load capacity of the agricultural gear reducer. The simulation was performed for the following three surface heat treatment methods: untreated gears, nitriding heat treatment, and induction hardening method, those mostly used for agricultural gear reducers. The load capacity of the gear reducer was simulated using the safety factor, limit bending stress, and limit contact stress of the gear. The simulation of the load capacity was conducted using KISSsoft commercial software for gear analysis. The main results of simulation test were as follows: first, the nitriding heat treatment resulted in the highest safety factor for bending stress, which was increased about 77% from those of the untreated gears. Second, the induction hardening was the highest safety factor for contact stress, which was increased about 150% from those of the untreated gears. The safety factor for contact stress of the induction hardening was increased about 64% from those of the nitriding heat treatment. The study result suggested that the surface heat treatments could enhance load capacity and that the method of surface heat treatment should be determined based on simulation results for appropriate use scenarios.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.4
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• pp.527-536
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• 2014

In this paper, the 50kW aerogenerator which is applicable to the microgrid was designed and analyzed by using commercial simulation program Maxwell 2D. Particularly, the suggested PMSG to reduce the cogging torque introduced the offset and skew concept. The suggested optimal value of offset and skew was decided by 2mm and 60 degree of electric angle. The simulation results of the PMSG when load operation condition showed the average harmonic distortion 1.3%, voltage 322.41V, current 94.95A, and iron loss 9.73W, eddy current loss 73.68W, copper loss 3.52kW. The capacity of aerogenerator calculated 61.56kW, and the suggested design process can be applied to higher capacity generator.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.99-111
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• 2010

Recently, a very large vessel's maneuvering performance, rudder performance and rudder design's importance is considered to be an important subject. There have been few studies on the design process of rudder device before. The aim of this paper is to investigate a design process of rudder device and to propose a generalized design process of rudder device. Firstly, we investigated the rudder device design process of Korean major shipyards. And the differences of a torque calculation method, rudder section design, maneuvering performance examination method, etc were analyzed theoretically. Secondly, the design process of rudder device was divided into concept design, initial design and detail design. In concept design, a rudder area was estimated and its validity was examined. In initial design, rudder profile and design method has been selected through rudder form determination process. And principal dimension and steering gear capacity were determined. Maneuvering performance was also examined by simulation tool. In detail design, design criteria considered in rudder initial design has been investigated thoroughly. Also a rudder torque, rudder cavitation performance and rudder structure analysis were estimated. And maneuvering performance was also examined by model test. Finally, based on the results of investigation, the design process of rudder device was generalized and proposed.

• Journal of Power System Engineering
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• v.12 no.1
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• pp.13-19
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• 2008

In this study, a variable induction and exhaust system is applied to turbocharged diesel engine to improve the volumetric efficiency, especially, in a low and transient engine speed range where much of the pollutant matters are expelled out. The volumetric efficiency is known as one of the most important factor which affects significantly engine performance, fuel economy and further emission and noise level. As the torque increase with the engine speed up, the gas flow in an exhaust pipe become pulsating and then has an effect on boost up capacity of air charging into the cylinder and expelling capacity to atmosphere simultaneously. But at a low and idling speed, the pulsation effect was not so significant. Accordingly, resonator was employed to compensate their loss. The variable induction system consists of the secondary pipe, resonator, intercooler, and torque variance were examined with extended operating conditions. In the mean time, for interpretation and well understanding for the phenomena of wave action that arising during intake and exhaust process between turbocharger and variable intake system, the concept of the combined supercharging was introduced. Some of results are depicted which deal with a pressure history during valve events of induction process. Consequently, by the governing of these phase and amplitude of pulsating wave, it enables us to estimate and evaluate for the intake system performance and also, designing stage of the system layout.

• Journal of Power Electronics
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• v.12 no.1
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• pp.49-57
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• 2012

This paper presents performance evaluation of an Integrated Starter-Alternator (ISA) prototype with an Interior Permanent Magnet (IPM) synchronous machine under sensor-less operation. To attain a high starting torque at zero speed and in subsequent extremely low speed range, a hybrid signal injection method is proposed. At higher speed, an improved stator flux observer is used for the stator flux estimation. This observer is able to produce accurately-estimated stator flux linkage for high performance Direct Torque and Flux Control (DTFC) implementation. The sensor-less DTFC IPM synchronous machine drive takes full advantage of the capacity of the power converter and fulfills the control specifications for the ISA. The trajectory control algorithm responds rapidly and in a well behaved manner over a wide range of operating conditions. The experimental results verify the feasibility and advantages of the system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.478-483
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• 2005

This paper presents the comparison analysis of a Journal and thrust FDB (fluid dynamic bearing) and a conical FDB in a HDD spindle motor. The Reynolds equation is appropriately transformed to describe journal, thrust and conical bearing. Finite element method is applied to analyze the FDB by satisfying the continuity of mass and pressure at the interface between the hearings. The pressure field of the bearings is numerically approximated by applying the Reynolds boundary condition. The load and friction torque are obtained by integrating the pressure and the velocity gradient along the fluid film. The flying height of the spindle motor is measured to verify the proposed analytical result. This research shows that the conical bearing generates bigger load capacity and less friction torque than the journal and thrust bearing in a HDD spindle motor.

• Journal of Power System Engineering
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• v.13 no.4
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• pp.11-17
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• 2009

This paper deals with the effects of pulsating flow on volumetric efficiency, which may be generated during the gas exchange procedure, due to piston motion, valve event on intake and exhaust stroke and unsteady flow of turbocharger of a three-cylinder four stroke turbo-charged diesel engine. Consequently, volumetric efficiency affects significantly the engine performance; torque characteristics, fuel economy and further to emission and noise level. As the expansion ratio became larger the engine speed varies and torque increases, the pressure pulsation in an exhaust gas pipe acts as an increasing factor of intake air charging capacity totally. The phase and amplitude of pressure pulsation in the intake system only affects volumetric efficiency favorably, if it is well matched and tuned effectively to the engine. Thus, to verify the exact phase and amplitude of the pressure variation is the ultimate solution for the air-flow ratio assessment in the intake stroke. Some experimental results of pressure diagrams in the intake pipe and gas-flow of turbine in-outlet are presented, under various kinds of operating condition.