• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.9-12
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• 2008

Mathematical singularities of circuit equations with three-phase ideal transformer connections are studied. Three-wired wye-wye connections, delta-delta connections, and primary four-wired wye-delta connections are singular. The matrices of their circuit equations have zeros in their eigenvalues. Three-wired wye-delta connections, wye-wye-delta connections, and primary four-wired wye-wye connections are not singular. The physical meaning of their singularities is that they are sensitive and prone to be ill-conditioned. Equivalent shunt admittances representing ion losses and magnetizing inductances make the singular matrices non-singular in wye-connected circuits. And, equivalent series impedances representing copper losses and leakage inductances make the singular matrices non-singular in delta-connected circuits. The tableau analysis is used for the study.

• Journal of Electrical Engineering and Technology
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• v.6 no.4
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• pp.527-534
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• 2011

In the present paper, the characteristics of Mega-Flux$^{(R)}$, JNEX-Core$^{(R)}$, amorphous and ferrite cores are compared to the inductor of buck-boost converters for Hybrid Electric Vehicles. Core losses are analyzed at the condition of 10 kHz sine wave excitations, and permeability fluctuations vs. temperature and magnetizing force will be analyzed and discussed. Under the specifications of the buck-boost converter for 20 kW THS-II, the power inductor will be designed with Mega-Flux$^{(R)}$ and JNEX-Core$^{(R)}$, and informative simulation results will be provided with respect to dc bias characteristics, core and copper losses.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.2
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• pp.278-285
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• 1994

Aging test was done by loading back method for 20kVA amorphous core transformers manufactured by Hyosung Industries Co. and korea Electric Power Corporation. Iron losses, copper losses and insulation oil temperatures of the transfromers was measured for all the testing period. Expected life of amorphous core transformers on the basis of the degradation of the insulators was 46 years at 100% load, and 2.4 years at 130% load. Average temperature rising of transformer oil of amorphous core transformers was higher than that of silicon steel core transformers. Hence lowering the oil temperature by optimized design is needed for improving the expected life of the amorphous transformers.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.563-565
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• 2005

This paper is proposed an efficiency optimization control algorithm for a synchronous reluctance motor(SynRM) which minimizes the copper and iron losses. ALso, this paper presents a sensorless control scheme of SynRM using artificial neural network(ANN). The proposed algorithm allows the electromagnetic losses in variable speed and torque drives to be reduced while keeping good torque control dynamics. The control performance of ANN is evaluated by analysis for various operating conditions. Analysis results are presented to show the validity of the proposed algorithm

• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.56-61
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• 2000

The precise and reliable loss model for induction motor and converter system is very important in order to predict the efficiency performance of variable speed drives. This paper proposes an accurate loss model of induction motor and converter system. The motor losses, such as stator and rotor copper loss, core loss and stray loss, are considered for fundamental and harmonic frequencies. Also considered are the skin effect on rotor resistance, temperature effect on bath stator and rotor resistance, magnetizing inductance saturation, and friction and windage loss. All the above features are incorporated in a synchronous frame dynamic d-q equivalent circuit. The converter system, consisting of a diode rectifier and PWM transistor inverter, is modeled accurately for conduction and switching losses. Validity of the models, in both steady state and transient conditions, is verified by simulations.

• Journal of Power Electronics
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• v.9 no.2
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• pp.243-258
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• 2009

Bearingless centrifugal pump systems are employed in the semiconductor, pharmaceutical and medical industries due to their facility for pumping high purity fluids without particle contamination. Two types of forces have to be generated by the stator units, namely bearing forces for achieving magnetic levitation, and drive forces for producing the needed pump torque. The generation of these forces requires bearing and drive windings, which can be realized as separate bearing and drive coils or as identical, combined coils on the stator claws. In this paper, a detailed comparison between these two winding concepts is undertaken, whereby the copper losses, the power electronics losses, and the achievable pump output pressure are evaluated for both concepts. For each criterion a ratio of improvement is calculated analytically which allows evaluation of the performance of the two winding concepts for any given pump operating point and design. Finally, also practical features such as control complexity, cabling effort and manufacturability are discussed and measurements on prototype systems are carried out to validate the considerations.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.93-95
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• 2008

Nowadays more attention is paid to the developing high efficiency electrical machines for energy saving and protection of natural resources. In general, the electromagnetic losses appearing in electrical machines are widely classified into copper loss, core loss and rotor loss. Particularly, in permanent magnet (PM) machines, core loss forms a larger portion of the total losses than in another machine. So, satisfactory prediction of core loss at the design or analysis stage of PM machines is essential to active high efficiency and high performance. This paper deals with analysis of magnetic field distribution due to geometry of stator core for magnetic core loss calculation of multi-pole PM synchronous machine.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1188-1194
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• 2008

To cope with the demagnetization risk of permanent magnets used in Interior Permanent Magnet Synchronous Motors(IPMSM), an accurate iron analysis and thermal analysis are very important. In this research, to calculate thermal increment of IPMSM for high-speed traction motor, we will extract losses of IPMSM considering the condition of field weakening control. Then we will input the calculated losses such as iron loss and copper loss as the thermal sources. Based on magnetic filed and thermal analysis, we will support the design of IPMSM for high-speed train.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.73-76
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• 1999

We have fabricated and tested a Bi-based high temperature superconducting current lead system. Ag sheathed Bi-2223 mono-filament tapes of $I_c=8.4$ A at 77 K under self-field condition were fabricated using powder-in-tube(P1T) method. Multi-layer current leads can be made by stacking of Ag sheathed Bi-2223 mono-filament wires. The critical current of this 10-layer current lead is about 68 A. The contact resistance across the copper-current lead interface has been studied using current-voltage characteristics. At temperature below critical temperature the resistive contribution of the interface to the total contact resistance dominates. We have measured AC transport losses in a current lead at 77 K, 60 Hz by a transport method.

• Journal of Magnetics
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• v.22 no.2
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• pp.196-202
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• 2017

The occurrence of ferroresonance in electrical systems including nonlinear inductors such as transformers will bring a lot of malicious damages. The intense ferromagnetic saturation of the iron core is the most influential factor in ferroresonance that makes nonsinusoidal current and voltage. So the nonlinear behavior modeling of the magnetic core is the most important challenge in the study of ferroresonance. In this paper, the ferroresonance phenomenon is investigated in a single phase transformer using the finite element method and considering the hysteresis loop. Jiles-Atherton (JA) inverse vector model is used for modeling the hysteresis loop, which provides the accurate nonlinear model of the transformer core. The steady-state analysis of ferroresonance is done while considering different capacitors in series with the no-load transformer. The accurate results from copper losses and iron losses are extracted as the most important specifications of transformers. The validity of the simulation results is confirmed by the corresponding experimental measurements.