• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.829-835
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• 2006

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 vibration 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 Power Electronics
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• 제19권3호
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• pp.794-802
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• 2019

Magnetic geared motors are driven using the same operating principle as conventional synchronous motors in which a magnetic gear is embedded. The magnetic geared motor is structurally similar to a magnetic gear. However, by applying currents to the stator coil, the high-speed rotor is rotated by a magnetic field and the low-speed rotor is rotated according to the gear ratio. In this paper, the operational principle of a magnetic geared motor and the magnetic flux density in its inner and outer air gaps are described. Then the magnetic flux density in the two air gaps is used to express a method for calculating the electrical and mechanical output. Results obtained with the analytical calculation method are compared with those of the finite element analysis. Finally, a prototype is used to verify the results of the analytical calculation and FEA.

• Journal of Welding and Joining
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• 제19권5호
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• pp.526-533
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• 2001

Induction heating of float metal products has an increasing importance in many applications, because it generates the heat within workpiece itself and provides high power densities and productivity. In this study, the induction heating of a steel plate to simulate the line heating is investigated by means of the Finite Element Analysis of the magnetic field and temperature distribution. A numerical model is used to calculate temperature distribution within the steel plate during the induction heating with a specially designed inductor. The effects of materital properties depending on the temperature and magnetic field are taken into consideration in an iterative manner. The simulation results show good magnetic field with experimental data and provide good understanding of the process. Since the numerical model demonstrates to be suitable for analysis of induction heating process, the effects of air gap and frequency on magnetic-flux and power-density distribution are also investigated. It is revealed that these process parameters have an important roles on the electro-magnetic field and power-density distribution governing the temperature distribution of the plate.

• 에너지공학
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• 제2권2호
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• pp.231-236
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• 1993

The feasibility of Magnetohydrodynamic(MHD) Ship Propulsion using Superconduction Magnets is reviewed in light of relent advances in high-temperature superconducting. The propulsion using a screw propeller in the noise reduction has it's own limitation. The epochal noiseless MHD propulsion method which does not have this disadvantage is studying nowadays. The subject of a marine MHD as propulsion has been examined before and was found to be interesting because of relatively low magnetic flux densities. It is demonstrated that the MHD propulsion is technically interesting with high magnetic flux density. The development of large-scale magnets using the high-temperature superconductor now under development could make it practical to construct submersibles for high-speed and silent operation.

• 한국전기전자재료학회논문지
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• 제15권9호
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• pp.822-829
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• 2002

This paper deals with the distribution characteristics of the current density and axial magnetic flux density for each slits made on the contact electrode in the vacuum interrupter with axial magnetic field type using 3-dimension finite element analysis. It has been known that the presence of an axial magnetic field parallel to the current flow in the arc plasma can increase the high current breaking capacity of vacuum interrupter by carrying out the arc plasma from constricted mode to diffusion mode. The axial magnetic field is created of itself by current flow in the segments of coil electrode behind the contact electrode. The analyzed results show that if the slits are made in the contact electrode, they can increase the current density and axial magnetic flux density in the contact electrode surface and at the gap distance, which is due to decrease the effect of eddy currents flowing in the contact electrode. The phase shift due to eddy currents, defined 3s time difference between the maximum value of current and axial magnetic field, is decreased still more by increasing the number of slits made in the contact electrode at the center point of gap distance. These results demonstrate that 3-dimension finite element analysis has a great deal of merits in the development and evaluation of new electrode at the design of vacuum interrupter.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.215-218
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• 2002

HTS motors and generators have some advantages over LTS machines because of higher operating temperature. Very low temperature nakes LTS machines need higher refrigeration cost and large facilities. However, HTS machines are expected to be comparable with conventional counterparts at smaller machine ratings than LTS generators in terms of efficiency and size. As the operating temperature increases, the magnetic flux density generated by HTS field coils decreases relatively. For example, 1000hp HTS synchronous motor developed in a few years ago has maximum field density of 1.5T. At this point, magnetic material used in conventional machines is able to pass magnetic flux easily with high permeability. In order to investigate the effect, we arranged magnetic core only inside of magnet vessel of a 100hp target machine. By way of FEM analysis, we concluded that the magnetic core can reduce amount of expensive BSCCO conductor so much.

• 한국초전도ㆍ저온공학회논문지
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• 제5권2호
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• pp.66-70
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• 2003

Transient magnetic diffusion process in a melt-cast Bi2Sr2CaCu20X(Bi-2212) tube was studied by experimental and numerical analyses. The transient diffusion partial differential equation is transformed into an ordinary differential equation by integral method. The penetration depth of magnetic field into a superconducting tube is obtained by solving the differential equation numerically. The results show that the penetration depth as a function of time which is somewhat different from the results by Bean's critical state model. The reason of the difference between the present results and that of Bean's model is discussed and compared in this paper. This experiment measure the magnetic flux density in the supercondutor after supply direct-current of Bi-2212 rounded by copper coil. This study was discussed of valid of a previous numerical solution which is compared by the penetrate time and the magnetic flux density difference of between the present results and the numerical solution.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제2B권3호
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• pp.125-132
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• 2002

PMSMS (permanent magnet synchronous motors) are widely used in industrial applications and home appliances because of their high torque to inertia ratio, superior power density, and high efficiency. For high performance control, accurate informations about the rotor position is essential. Sensorless algorithms have lately been studied extensively due to the high cost of position sensors and their low reliability in harsh environments. A novel position sensorless speed control for PMSMs uses indirect flux estimation and is presented in this paper. Rotor position and angular velocity are estimated by the proposed indirect flux estimation. Linkage flux and magnetic field flux are calculated by the voltage equations and the measured phase current without any integration. Instead of linkage flux calculation with integral operation, indirect flux and differential magnetic field are used for the estimation of rotor position. A proper rejection technique fur current noise effect in the calculation of differential linkage flux is introduced. The proposed indirect flux detecting method is free from the integral rounding error and linkage flux drift problem, because differential linkage flux can be calculated without any integral operation. Furthermore, electrical parameters of the PMSM can be measured by the proposed TCM (time compression method) for soft starting and precise estimation of rotor position. The position estimator uses accurate electrical parameters that are obtained from the proposed TCM at starting strategy. In the operating region, a proper compensation method fur temperature effect can compensate fir the estimation error from the variation of electrical parameters. The proposed novel position sensorless speed control scheme is verified by the experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.906-908
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• 2003

A Linear induction electromagnetic(EM) pump of liquid metal fast breeder reactor(LMFBR) is used for the purpose that the liquid metal of high temperature is transported by EM force. This paper evaluates magnetic flux density necessary for transporting liquid metal, using analytical model of the linear induction EM pump. Using the 2-D finite element method(2-D FEM), magnetic flux density is estimated in consideration of a geometric model, electric parameter, and velocity of liquid metal. From the viewpoint of hydrodynamics, the results can be used for flow analysis of the liquid metal.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.776-779
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• 2002

This paper describes the magnetizer design of highly saturated magnetic circuit by high external field. The magnetizer is loaded by a capacitor bank with impulse currents to reach high magnetic flux-density(typically 5[T]). Magnetizing current come out from magnetizing system is simulated by analytic method and transient FEM, also field distributions of the magnetizer are analyzed.