• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.810-811
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• 2015

In this paper, we investigate the optimization design for a spoke type motor with the characteristics of high torque density and high-efficiency. This motor has a high output per unit volume. In order to reduce noise and vibration caused by a high cogging torque, optimization design of the rotor and stator have been conducted using both Response surface method (RSM) and Finite elements method (FEM). In this paper, we show the potential for this motor to efficiently replace existing interior permanent magnet synchronous motors (IPMSM) in a wide range of industries.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.929-930
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• 2006

This paper presents a direct instantaneous torque control (DITC) of Switched Reluctance Moto (SRM) with a novel 4-level converter to obtain smooth torque and dynamic performance improvement. The DITC method can reduce the high inherent torque ripple of SRM drive system, but driving efficiency and dynamic performance are somewhat low due to the slow excitation current build-up. Since the 4-level converter can obtain a addition high voltage to get fast excitation current and demagnetization current, so, it can improve dynamic performance easily. As a high performance SRM drive system with low torque ripple and high dynamic performance can be implemented. The validity of proposed method is verified by some computer simulations and comparative experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.187-188
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• 2008

An ultrasonic motor of high torque with a new configuration for application in automobiles is proposed. The newly designed stator is a two sided vibrator consisting of a toothed metal disk with a piezoelectric ceramic ring bonded on both faces of the disk which generates a flexural traveling wave along the circumference of disk. In this configuration, the displacement on the surface of stator may not be confined. It also produces a large vibrating force and amplitude because the vibrator is sandwiched by two piezoelectric plates. It is possible to increase the torque by improving the vibration characteristics. To compute the vibration mode of the motor of diameter 48 mm, the finite element method was used. A 6th mode was chosen as the operation mode with a resonance frequency of about 64.4 kHz. According to this design and measured its performance, a prototype was fabricated. The performance measurement of the prototype motor showed that its stall torque was about 1.8 Nm and efficiency was 37% at 60% of the maximum torque.

• Journal of Power Electronics
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• v.11 no.4
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• pp.449-455
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• 2011

Electric drive vehicles (EDV) have received much attention recently because of their environmental and energy benefits. In an EDV, the motor drive system directly influences the performance of the propulsion system. However, the available DC voltage is limited, which limits the maximum speed of the motors. At high speeds, the inverter voltage increases if the square wave (SW) voltage (six-step operation) is used. Although conventional direct torque control (DTC) has several advantages, it cannot work in the six-step mode required in high-speed applications. In this paper, a single-mode seamless DTC for AC motors is proposed. In this scheme, the trajectory of the reference flux changes continuously between circular and hexagonal paths. Therefore, the armature voltage changes smoothly from a high-frequency switching pattern to a square wave pattern without torque discontinuity. In addition, because multi-mode controllers are not used, implementation is more straightforward. Simulation results show the voltage pattern changes smoothly when the motor speed changes, and consequently, torque control without torque discontinuity is possible in the field weakening area even with a six-step voltage pattern.

• Journal of Power Electronics
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• v.13 no.4
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• pp.546-551
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• 2013

This paper deals with the optimum design of the stator and rotor shape of the interior permanent magnet synchronous motors (IPMSM) that are used in applications for automobiles. IPMSMs have the following advantages: high power, high torque, high efficiency, etc. However, cogging torque which causes noise and vibrations is generated at the same time. The optimum design of shape of a IPMSM was carried out with the aim of reducing cogging torque. Six variables which affect to the performance of a IPMSM are chosen. The main effect variables were determined and applied to the response surface methodology (RSM). When compared to the initial model using the finite elements method (FEM), the optimum model highly reduces the cogging torque and improves the total harmonics distortion (THD) of the back-electro motive force (EMF). A prototype of the designed model was manufactured and experimented on to verify the feasibility of the IPMSM.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.1 s.118
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• pp.33-40
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• 2007

Rotatory two-phase transverse flux machine(TFM) is a relatively new type of motor with high power density, high torque, and low speed in comparison to conventional electrical motors. However, it has some shortcomings,.i.e. complex construction and high possibility of the magnetically induced nitration due to its inherent structure. This Paper investigates the characteristics of the magnetic force and the torque in the rotatory two-phase TFM by using the 3-D finite element method and the spectral analysis. This research shows that the average torque decreases and that the torque ripple increases as the phase delay increases. It also shows that the unbalanced magnetic force is one of the dominant excitation forces in this machine. And it proposes a new topology of rotatory two-phase TFM to eliminate the unbalanced magnetic force.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.157-168
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• 2008

Tightening of the screws in implant restorations should be accurate and precise. If applied torque is too low, screw loosening would be occurred. With too high torque, the screw fracture might take place. Various torque generating devices are developed and employed to apply a proper torque. The purpose of this investigation was to determine and compare the accuracy of the torque controllers. In this study, 4 types of torque controllers were used; electronic torque controller, torque limiting device, torque indicating device and contra angle torque driver. Digital torque gauge was employed to measure the de-torque value. Thirty cycles of tightening and loosening were done with each torque controller. All implant torque controllers have shown slight errors and deviations. The torque liming device exhibited the most accurate data. No significant difference was found among the mean de-torque values of the electronic torque controller, torque indicating device and contra angle torque driver. In the limitation of this study, it would be recommended that the implant torque controllers should be checked whether uniformed and precise torque can be generated and a measuring error should be corrected.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.5
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• pp.222-230
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• 2005

This paper deals with the reduction of cogging torque of a outer-rotor type BLDC motor mainly used for washing machines. The motor comprises permanent magnet outer-rotor and stator with coils and core. This structure inherently produces vibration and cogging torque because of uneven reluctance according to rotation of the rotor. Up to now, adopted a type of 24 magnet pole and 36 slot-stator. This generates high main torque but accompanies comparatively large cogging torque. This paper proposes a 32-pole 36-slot type motor which reduces cogging torque remarkably. The influence of cogging torque is varied according to pole-slot combinations. The characteristic of the motor was obtained by a two-dimensional finite element method coupled with a drive circuit. The performance of the proposed model is superior to that of the existing model because of the reduction of torque ripple and the improvement of back ernf wave form.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.971-981
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• 1994

In this paper, we consider feedback-linearizing control of VR (Variable Reluctance) motors which have been increasingly used in high performance direct-drive applications. We characterize all torque controllers that can make the generated torque of a VR motor linear to torque command but without torque ripple. The torque controlles maximize the range of torque commands which are admissible under the physical limitation in stator currents. The whole class of all such torque controllers is parameterized in the explicit form which contains a function to be chosen freely. This free function can be used to achieve other control objectives as well as linear dynamic characteristics. As the examples for optimal choices of the free function, we actually determine two optimal free functions, one for minimal rate of change in current commands and the other for minimal power loss due to stator resistance. To illuminate further the practical use of torque controllers proposed in this paper, we present some experimental results for the case of a commercially available VR motor.

• Journal of Magnetics
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• v.19 no.4
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• pp.393-398
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• 2014

This paper proposes new types of models that have coaxial magnetic gear (CMG) configurations to increase torque transmission capability. They have flux concentrating structures at the outer low speed rotor, and permanent magnets (PMs) are embedded in the space between stationary pole pieces. The torque performances of the proposed models are compared with those of a basic CMG model. The harmonic torque components due to air gap field harmonics are also analyzed to investigate the torque contribution of each harmonic by using finite element analysis (FEA) and the Maxwell stress tensor. The proposed CMG model is optimized to have high torque density with low torque ripples by response surface methodology (RSM). Compared to the basic CMG model, the proposed model has a huge increase in transmitted torque density, and is very advantageous in term of PM use.