• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.83-85
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• 2008

This paper deals with design and dynamic analysis of electromagnets for levitation applications. On the basis of equivalent magnetic circuit (EMC) method and 3-D finite element analysis (FEA) model, initial and detailed design for electromagnets are performed. Using the state equation for the closed-loop control, the dynamic analysis of electromagnets is also performed. Finally, this paper investigates the variation of levitation force according to current under fixed nominal air-gap, and the variation of required current according to load weight in order to maintain the nominal air-gap. From these results, the validation of design and dynamic analysis of electromagnets is confirmed. In particular, the influence of winding temperature on levitation control is discussed in detail.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.168-170
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• 1997

This paper presents the dynamic analysis of a reciprocating actuation system based on moving magnet actuator for gas compression. For the analysis of the linear actuator, an axisymmetric finite element method (FEM) considering the saturation effect of the magnetic material is used, and electrical circuit equation, mechanical dynamic equation and pressure dynamics are coupled. In the FE analysis, we adopt a moving line technique. The pressure dynamics of the gas in the compressor is modeled by using the law of thermodynamics. The analysis results are compared fairly well with experimental ones.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.884-885
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• 2007

This paper presents an window based user-friendly designed characteristics analysis program of permanent-split capacitor single-phase induction motor. For the analysis, equivalent magnetic circuit and symmetrical coordinate method are used. The saturation effect and iron loss of stator and rotor core are considered. The analysis program is made to GUI type which can be used easily by many elementary designer. The accuracy of analysis is verified by comparison with experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.125-130
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• 2007

Single-phase is used widely power of field of appliance because can use commercialized power directly without power transform. Specially, because condenser nu-drive style single-phase induction motor efficiency is excellent, and most suitable in embodiment as economical. It is established true that method by crossing self-discipline and method by revolving magnetic field are interpretation of net single-phase induction motor, but method to calculate electric motor inside proper move in existent theory or method is some complex. That arbor in the law of circuit constant that combine equivalent circuit law with numerical analysis law according to development of the latest computer or microprocessor is suggested and does the calculation processing fast and correct. In this paper, measurement wishes to present method that calculate after calculate digital measurement that measures correctly and measures impossible the first and the second leakage reactance and no-load test locked-rotor test, DC test and resistance measurement of stator winding in circuit parameter calculation program that is had for MatLab program individually in single-phase power.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.5
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• pp.423-430
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• 2009

Recently as the inactive response characteristics of the existing RCD used on low voltage power distribution system, so control of overload and electric short circuit faults, major causes of electrical fires, are not enough. Therefore, this paper confirms the unreliability of the existing RCD by electrical fault simulator and proposes a EFDPD by using semiconductor switching devices and a high precision current sensor (namely, reed switch) for the prevention of electrical disasters in low voltage power distribution system caused by overload or electric short circuit faults. The sensitive reed switch in the proposed EFDPD exactly detects the increased magnetic flux with the overload or the short current caused by a number of electrical faults, and the following, the self circuit breaker in EFDPD rapidly cuts off the system. The proposed EFDPD confirms the excellent characteristics in response velocity and accuracy in comparison with the conventional circuit breaker through various operation performance analysis. The proposed EFDPD can also prevent electrical disasters, like as electrical fires, which resulted from the malfunction and inactive response characteristics of the existing RCD.

• Journal of Power Electronics
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• v.19 no.1
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• pp.190-200
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• 2019

The flyback converter, which can be regarded as a nonlinear time-varying system, has complex dynamics and nonlinear behaviors. These phenomena can affect the stability of the converter. To simplify the modeling process and retain the information of the output capacitor branch, a special sampled-data model of a peak current-mode (PCM) controlled flyback converter is established in this paper. Based on this, its dynamic behaviors are analyzed, which provides guidance for designing the circuit parameters of the converter. With the critical stability boundary equation derived by a Jacobian matrix, the stable operation range with a varied output capacitor, proportional coefficient of error the amplifier, input voltage, reference voltage and slope of the compensation ramp of a PCM controlled flyback converter are investigated in detail. Research results show that the duty ratio should be less than 0.5 for a PCM controlled flyback converter without ramp compensation to operate in a stable state. The stability regions in the parameter space between the output capacitor and the proportional coefficient of the error amplifier are enlarged by increasing the input voltage or by decreasing the reference voltage. Furthermore, the ramp compensation also can extend to the stable region. Finally, time-domain simulations and experimental results are presented to verify the theoretical analysis results.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.219-224
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• 2016

In this paper, coupled-mode theory (CMT) is used to obtain a transient solution analytically for a wireless power transfer system (WPTS) when unit energy is applied to one of two resonators. The solutions are compared with those obtained using equivalent circuit-based analysis. The time-domain CMT is accurate only when resonant coils are weakly coupled and have large quality factors, and the reason for this inaccuracy is outlined. Even though the time-domain CMT solution does not describe the WPTS behavior precisely, it is accurate enough to allow for an understanding of the mechanism of energy exchange between two resonators qualitatively. Based on the time-domain CMT solution, the critical coupling coefficient is derived and a criterion is suggested for distinguishing inductive coupling and magnetic resonance coupling of the WPTS.

• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.88-93
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• 2008

The electromagnetic parameters of a permanent magnet synchronous motor (PMSM) such as the open load permanent magnet flux, d axis reactance $X_d$, and q axis reactance $X_q$, are most essential to the performance analysis and optimization design of the motor. Based on the numerical analysis of the 3D electromagnetic field, the three electromagnetic parameters of permanent magnet synchronous motors with U form interior rotor structures are calculated by FEA. The rules of the leakage coefficient and reactance parameters changing with the air gap length, permanent magnet magnetism length, and isolation magnetic bridge dimensions in the rotor are given. The calculated values agree well with the measured values. The FEA results are integrated with the self compiled electromagnetic design program to optimize the prototype motor. The tested performances of the prototype motor prove that the method is suitable for the optimization of motor structure.

• Journal of the Korean Solar Energy Society
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• v.23 no.3
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• pp.29-35
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• 2003

Generator for wind power can be either synchronous or asynchronous (induction) types. Induction and synchronous generators behave in a different way when subjected to severe faults. Induction generators does not have an angle stability limit and short circuit in the neighborhood of an Induction generator causes the demagnetization of the machine when the fault is cleared, the voltage raises slowly, while the grid contributes with reactive power to the generator and the magnetic flux recovers. On the other hand in the synchronous generators the recovery of the voltage is immediate, since the excitation of the rotor angle comes from an independent circuit. This paper shows the result of the transient state analysis in the network connected to wind generation system Several case studies have been conducted to determine the effect of the clearing time of a fault on the network stability. It has been found that the critical clearing time can be as low as 61ms in the case of induction generator compared to 370ms in the case of synchronous generator.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.730-735
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• 2012

This paper presents a method to design the waveform of a back electromotive force (back EMF) of an axial flux permanent magnet (AFPM) motor using printed circuit board (PCB) windings. When the magnetization distribution of permanent magnet (PM) is given, the magnetic field in the air gap region is calculated by the quasi three dimensional (3D) space harmonic analysis (SHA) method. Once the flux density distribution in the winding region is determined, the required shape of the back EMF can be obtained by adjusting the winding distribution. This can be done by modifying the distance between patterns of PCB to control the harmonics in the winding distribution. The proposed method is verified by finite element analysis (FEA) results and it shows the usefulness of the method in eliminating a specific harmonic component in the back EMF waveform of a motor.