• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.815-816
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• 2006

This paper proposes a novel design method for flux barrier which built in q-axis in rotor of IPM type BLDC motor. It aims to reduce the motor vibration with reduced cogging torque and lessened torque ripple by the sinusoidal waveform distribution of flux generated in the permanent magnet, which results from designed flux barriers. Design of flux barrier optimized using the Taguchi methods that considered multiple quality characteristics, such as cogging torque, average torque and efficiency are considered. The result of proposed method is compared and verified with 2D finite element method (FEM).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.60 no.1
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• pp.80-86
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• 2024

We analyzed the performance of hubless rim propellers based on the number of blades, maintaining a fixed pitch ratio and expanded area ratio, using computational fluid dynamics (CFD). Thrust coefficient, torque coefficient and efficiency according to the number of blades were analyzed. In addition, the pressure distribution on the discharge and suction sides of the blade was analyzed. As the advance ratio increases, the thrust coefficient decreases. The highest thrust was shown when the advance ratio was lowest. For the three, four, five and six-blades, the torque coefficient tended to decrease as the advance ratio increased. In the case of seven and eight-blades, the torque coefficient tended to increase as the advance ratio increased. The maximum efficiency was found when the advance ratio was 0.8. When the three-blade, it showed high efficiency at all advance ratios. A high pressure distribution was observed at the leading edge of the discharge blade, and a low pressure distribution was observed at the trailing edge. Applying a hubless rim-driven thruster with the three-blade can generate higher thrust and increase work efficiency.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.12
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• pp.1073-1080
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• 2015

A drive shaft is used to transmit torque and rotation through the connection of components of a drive train. Recently, a monobloc drive shaft without welding regions is developed to improve the safety of the drive shaft. The drive shaft bears the shear stress induced by torque. The objective of this paper is to investigate into the structural safety of a monobloc tubular drive shaft subjected to torque. Elasto-plastic finite element (FE) analysis is performed to estimate the deformation behavior of the drive shaft and stress-strain distribution in the drive shaft. Several techniques are used to create finite element (FE) model of the monobloc tubular drive shaft subjected to torque. Through the comparison of the results of FE analyses with those of experiments from the viewpoint of rotational angle, appropriate correction coefficients for different load conditions are estimated. The safety of the tubular drive shaft is examined using the results of FE analyses for different load conditions. Finally, it is noted that the designed tubular drive shaft has a sufficient structural safety.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.3
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• pp.85-91
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• 2007

This study was carried out to minimize the lifting force of a two hinge type stand mechanism. This unit is designed for the display devices in order to enhance the ergonomics for effective height adjustment and maintenance at any preferred position. The unit will be very useful for the mechanism fabricated with a coil spring and disc springs as a torque generator. The maximum and the minimum torque value should be calculated initially for the smooth lift. And the reasonable torque distribution is necessary to prevent any auto lift and auto dropping at any position because the torque generated by coil spring is more sensitive than disc spring in tilting the position. Therefore, the analysis of the coil spring is requisite to issue the specific torque value depending on the distorted angle with securing reliability of a long time storage condition. After the theoretical torque value was calculated, the evaluation was carried out by making a proto-type sample, then distorted angle was updated by experiment. The result of this study can readily be applied to various units for the optimization of the smooth lift.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1454-1457
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• 2003

This study was carried out to minimize the lifting force of a two hinge type stand mechanism. This unit is designed for the display devices in order to enhance the ergonomics for effective height adjustment and maintenance at any preferred position. The unit will be very useful for the mechanism fabricated with a coil spring and disc springs as a torque generator. The maximum and the minimum torque value should be calculated initially for the smooth lift. And the reasonable torque distribution is necessary to prevent any AUTO LIFT and AUTO Drooping at any position because the torque generated by coil spring is more sensitive than disc spring in tilting the position. Therefore, the analysis of the coil spring is requisite to issue the specific torque value depending on the distorted angle with securing reliability of a long time storage condition. After the theoretical torque value was calculated, the evaluation was carried out by making a proto-type sample, then distorted angle was updated by experiment. The result of this study can readily be applied to various units for the optimization of the smooth lift.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.3
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• pp.80-87
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• 2012

This paper suggests the slot wedge shape for reducing the cogging torque of a direct-drive permanent magnet synchronous generator for a bike. To consider easy coil winding, we applied a structure of open slot for the permanent magnet synchronous generator (PMSG). Because the cogging torque of PWSG with the open slot is very large, we are designed the appropriate specifications of the PMSG by selected the appropriate material of slot wedge and various slot wedge shapes. The prototype model is selected by design theory for reducing cogging torque and maximizing efficiency of PMSG. And the detailed structure design of the model was designed by the loading distribution method. The PMSG models were analyzed by finite element method. Finally, we have suggested appropriate material of slot wedges and its shape which has benefit to further reducing cogging torque and preventing decreasing of the generating power.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1535-1540
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• 2013

In this paper, the Radial Magnetic Force(RMF) and cogging torque which cause vibration and noise in IPM type BLDC motor were analyzed. The cogging torque and RMF cause electromagnetic vibration. So, a notch was installed for the equilibrium of RMF and cogging torque reduction. The notch was analyzed by using a Fourier Series for the energy distribution of the air-gap. The equilibrium of RMF and the reduction of cogging torque were performed by a Design Of Experiment(DOE) with the notch. Also, operating characteristics and efficiency were analyzed and compared.

• Proceedings of the KIEE Conference
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• 2006.10b
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• pp.147-153
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• 2006

Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.498-505
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• 2007

This paper proposes the novel flux barrier that built in q-axis in rotor of IPM type BLDC motor. The novel flux barrier aims to reduce the motor vibration with reduced cogging torque and lessened torque ripple by the sinusoidal waveform distribution of the flux generated in the permanent magnet. For optimization of the novel flux barrier, the Taguchi method is effectively employed which considered multiple objective quality characteristics, such as cogging torque, average torque and efficiency. The result of proposed model compare with the initial model and it is verified by 2D finite element method (FEM) results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.7
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• pp.26-31
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• 2011

In this paper, torque characteristics analysis of Synchronous Reluctance Motor with the cylindrical rotor type by winding function theory(WFT) is described. The stator is same as one of the induction motor. From the d-axis, q-axis flux density distribution, to calculate self and mutual inductances needed to calculate the torque of the machine by using winding function theory the new equivalent geometry of rotor was proposed. D-axis, q-axis flux densities, self inductance and torque characteristics were obtained. From the comparison with results of finite element analysis the proposed method was verified.