• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.754-756
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• 1987

In this paper, a new Harmonic Torque Factor(HTF) that represents torque ripple of induction motor is proposed. Trapezoidal PWM is analyzed to torque ripple by HTF and than we obtain optimum triangular factor at some carrier ratio. Six-step, sinusoidal PWM and Trapezoidal PWM are compared and evaluated for choosing a good control strategy of PWM inverter. It turns out that six-step inverter is better than sinusoidal PWM and Trapezoidal PWM when their carrier ratio is 9, and Trapezoidal PWM is superior to sinusoidal PWM. At induction motor is driven by PWM inverter, torque ripples are investigated by computer simulation using d-q two axis model. It is proved that a new Harmonic Torque Factor ix valid.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권2호
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• pp.1-8
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• 2001

This paper deals with magnetic field analysis and computation of cogging torque using an analytical method in Interior Permanent Magnet Motor (IPMM). The magnetic field is analyzed by solving space harmonics field analysis due to magnetizing and the cogging torque is analyzed by combining field analysis with relative permeance. In reducing cogging torque, the inferences of various design variable and magnetizing distribution are investigated. It is shown that the slot and pole ratio (the pole-arc / pole-pitch ratio) combination has a significant effect on the cogging torque and presents a optimal flux barrier shape to reduce the cogging torque. The validity of the proposed technique is confirmed with 2-D Finite Element(FE) analysis.

• 생명과학회지
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• 제18권1호
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• pp.30-37
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• 2008

본 연구에서는 남자 고등부 태권도 선수들을 대상으로 하여 등장성운동과 등척성 등장성운동을 혼합하여 복합 훈련을 실시한 차이를 알아보기 위하여 등속성 근 기능 중 최대우력, 동측근력비율, 양측근력비율, 근지구력을 분석한 결과를 다음과 같은 결론으로 나타내었다. 첫째, 최대우력은 좌우측 신굴근 모두에서 등장성 운동집단에 비하여 복합 훈련집단이 유의하게 증가한 것으로 나타났다. 둘째, 동측근력비율, 근지구력은 두 집단 간에 유의한 차이는 나타나지 않았지만, 운동전후에 차이에 있어서는 두 집단 모두 유의하게 증가하였다. 셋째, 양측근력비율은 두 집단 간에 유의한 차이는 나타나지 않았지만, 운동전후에 차이에 있어서는 두 집단 모두 유의하게 감소하였다. 이러한 결과로서 태권도 선수들의 경기력 증가를 위한 주요 체력요소인 평형능력, 근 지구력의 향상을 위한 방법으로 등장성 운동과 복합훈련 중 어떠한 방법으로 실시하여도 근 기능을 향상 시킬 수 있는 운동법으로 생각된다. 그러나 등척성 운동과 등장성 운동을 복합적으로 실시하였을 경우 최대우력이 등장성운동을 실시한 집단에 비하여 유의하게 증가하는 현상으로 보면 태권도 발차기의 파워를 보다 증가시키기 위해서는 등장성 운동과 등척성을 복합적으로 실시하는 운동방법이 보다 효과적인 방법으로 생각된다.

• 오토저널
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• 제12권3호
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• pp.9-20
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• 1990

The speed ratio-torque load-axial force characteristics of a rubber V-belt (RVB) and a metal V-belt (MVB) CVT are investigated and their performances are compared. It is found that power is transmitted by tension difference in RVB, and by thrust difference in MVB. The nondimensional equations for speed ratio-torque load-axial force of RVB are exactly same as those of MVB. However, actual characteristics of axial forces of RVB and MVB are different depending on their power transmission methods. The torque capacity of MVB is 5-6 times higher than that of RVB due to MVB's higher strength, even if the required axial force of MVB CVT control is 3-4 times higher than that of RVB.

• 대한기계학회논문집
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• 제14권2호
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• pp.349-357
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• 1990

Power transmission characteristics and speed ratio-torque load-axial force relationship for a metal V-belt CVT were investigated theoretically and experimentally. In the metal V-belt CVT drive, it was found that the power was transmitted by thrust force and that band tension should be greater than compression force between the metal blocks. The experimental results for the speed ratio-torque load-axial force relationship showed good agreement with those predicted using equations developed from theoretical considerations.

• 대한기계학회논문집A
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• 제33권5호
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• pp.463-468
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• 2009

Torsional oscillations of the drivetrain in electric vehicles are generated under rapid driving conditions. These lead to an uncomfortable jerking of the vehicle and an increased stress of the mechanical components. To suppress torsional oscillations, the low pass and notch filters between the torque command from the acceleration pedal and electric motor input torque are suggested. The filter parameters are optimized based on Taguchi method with $L_{18}(3^5)$ orthogonal array. The signal to noise (S/N) ratio mainly depends on slew rate of motor input torque, damping ratio and natural frequency of notch filter. With the proposed suppression control scheme, the S/N ratio is shown to be increased by 4.7dB and the torque overshoot of the drive shaft is reduced to 30%.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.71-76
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• 2009

This study was conducted to investigate the load acting on a tractor engine when it delivers the maximum power at drawbar. The results of the drawbar tests on the 5 locally-made and 14 imported tractors conducted at NIAE in 2004, and the 15 tractors tested at OECD test stations in foreign countries were analyzed and presented by the torque load ratio, defined as a ratio of the engine torque load caused by drawbar pull to its full-load capacity, as a function of pull speed. The NIAE test results showed that the torque load ratio increased from 20 to 80% with pull speed less than 5 km/h. At speeds faster than 5 km/h, it was 80${\sim}$110% regardless of the pull speed. However, the OECD test results showed that the torque load ratio was evaluated mostly to be 70${\sim}$90% in the entire pull speed range. The same trend was also shown for the maximum drawbar load. The difference in the torque load ratio may be attributable to bias-ply tires for locally-made and some imported tractors. It is also suggested that the input torque load may be increased safely up to 120% of the full load capacity of the tractor engine for an accelerated life test of tractor transmissions.

• 대한기계학회논문집B
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• 제30권3호
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• pp.278-286
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• 2006

Experiments were conducted to estimate the performance of drag force type vertical axis wind turbine with an opening-shutting rotor. It was operated by the difference in drag force generated on both sides of the blades. The rotational speed was measured by a tachometer in a wind tunnel and the tunnel wind speed was measured by using a pilot-static tube and a micro manometer. The performance test for a prototype was accomplished by calculating power, power coefficient, torque coefficient from the measurement of torque and rpm by a dynamometer controller. Various design parameters, such as the number of blades(B), blade aspect ratio(W/R), angle of blades$(\alpha)$ and drag coefficient acting on a blade, were considered for optimal conditions. At the experiment of miniature model, maximum efficiency was found at N=15, $\alpha=60^{\circ}$ and W/R=0.32. The measured test variables were power, torque, rotational speed, and wind speeds. The data presented are in the form of power and torque coefficients as a function of tip-speed ratio V/U. Maximum power was found in case of $\Omega=0.33$, when the power and torque coefficient were 0.14 and 0.37 respectively. Comparing model test with prototype test, similarity law by advance ratio for vertical axis wind turbine was confirmed.

• 한국자동차공학회논문집
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• 제9권1호
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• pp.112-121
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• 2001

In this paper, an engine-CVT integrated control algorithm is suggested by considering the powertrain loss, inertia torque and the CVT ratio response lag. The integrated control algorithm consists of (1) the optimal engine power calculation and (2) determining of the optimal throttle valve opening and the optimal CVT ratio. The optimal engine power is obtained by compensating the inertia torque due to the CVT ratio change and the powertrain loss that is calculated iteration procedure. In addition, an algorithm to compensate the effect of the CVT ratio response lag on the drive torque is suggested by the engine speed compensation causing the increased optimal CVT ratio. Simulation results show that the engine-CVT integrated control algorithm developed in this study makes it possible to obtain better engine operation on the optimal operating line, which results in the improved fuel economy while satisfying the driver's demand.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.339-341
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• 1999

This paper presents the gear ratio of wobble motor, accounting for finite friction in contact point. The gear ratio of a wobble motor is affected by rotor slip, which is a function of motive torque, excitation angle, and friction torque. The gear ratio of a wobble motor can be expressed as a constant term plus a term that accounts for rotor slip. The ideal gear ratio is constant term and is equal to the rotor radius divided by the distance between the center of the rotor and the center of the stator. The rotor-slip term is shown to be directly proportional to the contact point friction torque and inversely proportional to the square of the excitation voltage.