• Journal of Magnetics
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• v.16 no.4
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• pp.374-378
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• 2011

Axial Field Permanent Magnet (AFPM) generators are widely applied for the small wind turbine because of the higher power density per unit weight than that of the conventional radial field generator. It is caused by the disc shaped rotor and the stator structures. The generally used AFPM generator, AFER-NS generator, is composed of the two side's external rotors and non-slotted stator without stator core. However, the output voltage and the output power are limited by the large reluctance by the long air-gap flux paths. In this paper, the design study of AFIR-S generator having double side's slotted stator core is accomplished to improve the output generation characteristics. The electromagnetic design analysis and the design improvement of the suggested AFIR-S generator are studied. Firstly, the electromagnetic design analysis was done to increase the power density. Secondly, the design optimizations of the rotor pole-arc ratio of permanent magnet are accomplished to increase the output power and to reduce the cogging torque. Finally, the output performances of AFER-NS and AFIR-S generator are compared with each other. For this study, 3D FEA is applied for the design analysis because of three dimensional electromagnetic structures.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.812-813
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• 2011

This paper presents the characteristic of newly developed electrical steel and motor performance analysis for HEV/EV. This material is developed and optimized for high frequency operation to reduce the core losses in traction motors to increase fuel efficiency. Four types of electrical steel are introduced, which are optimized for high flux density (PNHF), high frequency low core loss (PNF), high punchability (PNS) and high strength (PNT) to meet different specifications from different types of traction motors. To identify the motor performance with this material, finite element analysis was used to calculate core loss as well as Ld and Lq for efficiency map. Also structure analysis was performed to calculate stress on bridge rotor.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.630-635
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• 1998

This paper establishes in a new unified manner new mathematical models with core(iron) loss factor for two kinds of AC motors, induction and synchronous motors which are supposed to generate torque precisely or/and efficiently under vector controls. Our new models consist of three basic equations consistent with the others such as differential equation describing electromagnetic dynamics, torque equation describing torque generating mechanism, energy transmission equation describing how injected energy is wasted, saved or transmitted where all vector signals are defined in general frame of arbitrary instant angular velocity. It is clearly shown in our models that equivalent core-loss resistance can express appropriately and separately both eddy-current and hysteresis losses rather than mere vague loss. Proposed model of induction motor is the most compact in sense of the number of employed interior states and parameters. This compact model can also represent eddy-current and hysteresis losses of rotor as well as stator. For synchronous motor, saliency is taken into consideration. As well known model for cylindrical motor can be obtained directly from salient one as its special case.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1269-1274
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• 2012

In this paper, the iron loss was calculated using estimated iron loss coefficient at 650W Interior Permanent Magnet Synchronous Motor(IPMSM) and 250W IPMSM. The iron loss coefficients was estimated different according to electrical steel material used to stator and rotor core in motor. Aspect of The rotating flux field and alternating flux field was confirmed by magnetic field behavior and harmonic analysis in stator core, the iron loss was calculated using flux density by Finite Element Method(FEM) and estimated coefficients by iron loss coefficient estimation proposed in this paper. The iron loss experiment was performed for verified to iron loss calculation, and the iron loss coefficients were verified by comparison of iron loss calculation value and experimental value.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.7
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• pp.75-80
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• 2014

The small wind turbines has the merits of setting up with low costs by individuals, and get the energy saving effects that, it has the secured, separate markets from the big range systems, and the developing of it is continuously proceeding. The objective of this paper is to provide the design characteristics analysis of a permanent magnet synchronous generator(PMSG) skewed for magnet of rotor, the main advantage to be explored with the use of a split core design is the reduction in manufacturing costs and its simplicity in manufacture, compared to the manufacturing costs of a core skew PM machine. This thesis is aiming mainly analyzing the characteristics of the prototype to verify through Finite Element Method(FEM) and tests.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.360-367
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• 1999

An inverter-driven induction motor is used as the traction motor for a high speed drive system that required safety, reliabillity, performance, compact size owing to the space and weight alloted for attaching to train, etc. particularly it is possible to happen the saturation effects of flux density at constant voltage-frequency region and then increase very higher than the at lowed capacity of no-load current and temperature in any case. therefore the optimum design of core, optimum voltage-frequency ratio, adoption of high grade magnetic core have been developed and researched for preventing these problems. this paper show the saturation effects of traction rotor by measuring the induced voltage of search coil at stator teeth and presents optimum voltage-frequency ratio as well as optimum core design through the comparison with efficiency, power factor, load current and no-load current for korea high speed train.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.790-798
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• 2008

Counter-rotating axial flow fan(CRF) consists of two counter-rotating rotors without stator blades. CRF shows the complex flow characteristics of the three-dimensional, viscous, and unsteady flow fields. For the understanding of the entire core flow in CRF, it is necessary to investigate the three-dimensional unsteady flow field between the rotors. This information is also essential to improve the aerodynamic characteristics and to reduce the aerodynamic noise level and vibration characteristics of the CRF. In this paper, experimental study on the three-dimensional unsteady flow of the CRF is performed at the design point(operating point). Flow fields in the CRF are measured at the cross-sectional planes of the upstream and downstream of each rotor using the $45^{\circ}$ inclined hot-wire. The phase-locked averaged hot-wire technique utilizes the inclined hot-wire, which rotates successively with 120 degree increments about its own axis. Three-dimensional unsteady flow characteristics such as tip vortex, secondary flow and tip leakage flow in the CRF are shown in the form of the axial, radial and tangential velocity vector plot and velocity contour. The phase-locked averaged velocity profiles of the CRF are analyzed by means of the stationary unsteady measurement technique. At the mean radius of the front rotor inlet and the outlet, the phase-locked averaged velocity profiles show more the periodical flow characteristics than those of the hub region. At the tip region of the CRF, the axial velocity is decreased due to the boundary layer effect of the fan casing and the tip vortex flow. The radial and the tangential velocity profiles show the most unstable and unsteady flow characteristics compared with other position of rotors. But, the phase-locked averaged velocity profiles of the downstream of the rear rotor show the aperiodic flow pattern due to the mixture of the front rotor wake period and the rear rotor rotational period.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.2
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• pp.295-310
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• 2015

In the present study, an unstructured mixed mesh flow solver was used to conduct a numerical prediction of the aerodynamic performance of the S-76 rotor in hover. For the present mixed mesh methodology, the near-body flow domain was modeled by using body-fitted prismatic/tetrahedral cells while Cartesian mesh cells were filled in the off-body region. A high-order accurate weighted essentially non-oscillatory (WENO) scheme was employed to better resolve the flow characteristics in the off-body flow region. An overset mesh technique was adopted to transfer the flow variables between the two different mesh regions, and computations were carried out for three different blade configurations including swept-taper, rectangular, and swept-taper-anhedral tip shapes. The results of the simulation were compared against experimental data, and the computations were also made to investigate the effect of the blade tip Mach number. The detailed flow characteristics were also examined, including the tip-vortex trajectory, vortex core size, and first-passing tip vortex position that depended on the tip shape.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.3
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• pp.241-247
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• 2014

The voltage source PWM inverter generally used to drive the air conditioning (A/C) fans has been posing a large issue that the bearings in air conditioning fan motors are highly possible to be corroded electrically. Potential difference called shaft voltage is generated between inner and outer rings of the bearings due to inverter switching. The shaft voltage causes bearing lubricant breakdown dielectrically. As a result, bearing current is caused. This current causes the bearing corrosion. In previous work, we demonstrated that the shaft voltage can be reduced by using an insulator inserted between the outer and inner cores of the rotor in an air conditioning fan motor without grounding. This paper proposes the other countermeasure for reducing the shaft voltage in fan motors. The countermeasure which adds a capacitor between the brackets and the stator core is effective even for fan motors with non-insulated rotor. The effectiveness is confirmed by both simulated and experimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.686-695
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• 2009

Flow characteristics in linear axial cascade have been studied using large eddy simulation(LES) based on finite element method(FEM) to investigate details of the leakage flow in the tip clearance of axial flow rotor. STAR-CD(FVM) and PAT-Flow(FEM) have been adopted to solve the Navier-Stokes equations for the simulation of the unsteady turbulent flow. Numerical results from the present study have been compared with the existing experimental results to investigate a tip clearance effect on velocity profile and static pressure distribution on blade surface at various spanwise positions. Both simulation results agree well with the experimental data. However, it has been shown that the results of finite-element large-eddy simulation agree better with experimental data than $k-{\varepsilon}$ turbulent model based on finite volume method regarding the tip vortex geometry and static pressure distribution at the center of the tip vortex core. As a result of this study, it is shown that finite-element large-eddy simulation method can predict more exactly on the tip leakage vortex flow and behind flow field.