• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1883-1890
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• 2017

Transformers are one of the most precious elements of the electric power system. Stability and reliability of the electric power network mainly depend on the working of the transformer. Leakage reactance of the transformer is one of the important factors and accurate calculation of the leakage reactance is necessary for the transformer designers and electric distributors. Leakage reactance of the transformer depends on the geometry of the transformer. There are many different methods for the calculations of the leakage reactance however mostly are usable when the axial heights of the high voltage and low voltage windings are equal. When the axial heights of high voltage and low voltage windings are asymmetric most of the analytical methods are not reliable. In this study, a new analytical method is introduced for the calculation of the leakage reactance. Fourteen different transformers are investigated in this study and four of them are presented in this paper. The results of the new analytical method are compared with the experimental results. Other analytical and numerical methods are also compared with this new method. Results show that this method is more reliable and accurate as compared to the other analytical methods. The maximum relative error between short-circuit test and proposed method for these fourteen transformers was less than 2.8%.

• Journal of electromagnetic engineering and science
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• v.1 no.2
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• pp.176-181
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• 2001

This paper presents the farced resonant characteristics of an electrically small cavity partially filled with dielectric material. The method of moments with Galerkins procedure is used to determine the farced resonant characteristics of the small cavity. In order to obtain the equations of the external reactance gives rise to the farced resonance at a given frequency, the cavity with external reactance can be treated as two-port network which has the admittance parameters. Numerical results show that the forced resonance, series or parallel resonance, can be obtained by the controlling the external reactance. To verify the availability of the theoretical analysis, experiments are carried out for the bakelite as the material by measuring the length of external reactance at operating frequencies.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.6
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• pp.44-49
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• 1974

reactance modulator composed of multi-stage phase modulator utilizing VVC diodes as variable reactance elements and an oscillartor-modulator, utilizing a VVC diode as a tuning element, coupled to a crystal resonator through an artificial λ/4 network are introduced and their characteristics as FM modulator are compared mutually from the practical view points. especially, to get high modulation sensitivity of reactance modulators using VVC diodes, making a multi-stage modulation distortion characteristics of multi-stage modulator was necessary. The harmonic moj\dulationdistorion characteristics of multi-stage reactance modulator is analized in detall. Multi-stage reachance modulator is preferable to maintain sufficiently stable carrier frequency over the wide range of temperature and a mobile-transceiver was made through this method. On the other hand, FM-Quartz oscillator using a VVc diode is suitavle for handy-talkies of good quality were made through this method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.184-184
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• 2012

We proposed a new measurement method of cutoff probe using the reactance spectrum of the plasma in cutoff probe system instead of transmission spectrum. The high accurate reactance spectrum of the plasma which is expected in previous circuit simulation of cutoff probe [1] was measured by using the automatic port extension method of the network analyzer. The measured reactance spectrum is good agreement with E/M wave simulation result (CST Microwave Studio). From the analysis of the measured reactance spectrum based on the circuit modeling, not only the electron density but also electron-neutral collision frequency can be simply obtained. The obtained results of electron density and e-n collision frequency were presented and discussed in wide range of experimental conditions, together with comparison result with previous methods (a previous cutoff probe using transmission spectrum and a single langmuir probe).

• 전기의세계
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• v.22 no.1
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• pp.42-51
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• 1973

The contriving equivalent circuit of single phase induction motor which does not separate the primary leakage reactance and the secondary leakage reactance by the revolving field theory, and the graphically calculating method of the characteristics with T-type circle diagram of three phase induction motor which does not suppose the primary leakage reactance can be drawn up only by the no load test, the lock test, and measuring the resistance of stator winding are suggested in this paper. The method which can calculate the parameters of the equivalent circuit and the characteristics with no load test, lock test and measuring resistance of stator windings is suggested in this paper. Considered the exciting current in lock test, we could calculate very accurate characteristics of the single phase induction motor.

• Journal of electromagnetic engineering and science
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• v.5 no.3
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• pp.105-111
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• 2005

This paper presents the basic characteristics of a cutoff cavity-backed aperture antenna with a feed post and a parasitic post inserted parallel to the aperture. It is shown that this type of antenna forcibly resonates the cutoff cavity by adding a single external reactance to the parasitic post. The Galerkin's method of moments is used to analyze integral equations for the unknown electric current on each post and the aperture electric field on the aperture. The value of an external reactance for forced resonance is analytically obtained by deriving a determining equation. Also the current distribution on each post, aperture electric field distributions, and the radiation patterns are discussed. The theoretical analysis is verified by the measured return loss and radiation patterns.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.2
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• pp.142-148
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• 1990

This paper deals with the desing method of Superconducting AC Generator (SCG). The establishment of design principle and design procedure of SCG are included in this study. Electric characteristics of SCG, such as synchronous reactance and sub-sub-transient reactance, are specified first as constraints and the size of SCG is calculated. Synchronous reactance and sub-sub-transient reactance are important factors because they determine the steady state and transient characteristics of SCG, respectively. A 20KVA SCG with double-shielded single-rotor is chosen for the case study. The design procedure proposed in this papar will also be applicable to large scale generators.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.135-142
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• 2016

Generally, closed slots are adopted to reduce the water friction loss in both the stator and the rotor of water filling submersible motor due to the special environment of operation. One of the obvious differences between the traditional induction motors and water filling submersible motors is that the submersible motors only need relatively smaller starting torque. This paper aims to analyze the slot leakage reactance of water filling submersible motor during starting transient operation. An improved analytical method which considered the magnetic saturation of the slot bridge and the skin effect of rotor bars is proposed. The slot permeance factor which has a direct impact on the slot leakage reactance is calculated. Then finite element models with different stator slot types are constructed and search coils are introduced to measure the slot flux linkage. Moreover, the starting performances of the models with two typical stator slots are compared and the flux leakage characteristics are obtained. Finally, the results obtained by finite element method are very close to the results obtained by analytical method.

• Journal of electromagnetic engineering and science
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• v.1 no.1
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• pp.37-42
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• 2001

This paper presents the basic characteristics of a cutoff cavity-hacked slot antenna, for the application of spacetenna, with a feed post and a parasitic post inserted parallel to the slot. This type of antenna might effectively excite the slot and forcibly resonate the cavity by adding external reactance to the parasitic post. The Galerkin\`s method of moments is used to analyze integral equations for the unknown electric current on each post and electric field in the slot. The value of external reactance for forced resonance is discussed by deriving a determining equation, the current distribution on each post and the radiation patterns are considered. The analysis is in excellent agreement with the experiment for the radiation patterns.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.5
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• pp.459-467
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• 1992

This paper presents a new algorithm for the countermeasure to alleviate the line overloads due to contingency without shedding loads in a power system. This method for relieving the line overloads by line switching is based on obtaining the kine outage distribution factors-the linear sensitivity factors, which give the amount of change in the power flow of each line due to the removal of a line in a power system. There factors are made up of the elements of sparse bus reactance matrix and brach reactances. In this paper a fast algorithm and program is presented for obtaining only the required bus reactance elements which corresponds to a non-zero elements of bus admittance matrix, and elements of columns which correspond to two terminal buses of the overloaded(monitored) line. The proposed algorithm has been validated in tests on a 6-bus and the 30-bus test system.