• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.1
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• pp.45-49
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• 2014

Torque of an induction motor is generally calculated by simplified equivalent circuit. However, the torque has an error since it is calculated by simplified equivalent circuit. In this paper, stator and rotor currents, torque, efficiency, and power factor are derived from the equivalent circuit of an induction motor using mesh analysis method. Then, they are compared with those calculated from simplified equivalent circuit.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.1
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• pp.109-112
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• 2013

It is well known that the maximum torque of a 3-phase induction motor does not vary as the resistance of rotor varies by proportional shifting. However, proportional shifting is derived using simplified equivalent circuit of induction motor. Therefore, there are some errors in the torque characteristics shown in the text book. This paper presents the torque characteristics using not simplified equivalent circuit but equivalent circuit. Errors produced by simplified equivalent circuit are presented.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1099-1105
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• 2006

In this paper, the equivalent circuit model of a Rosen-type multilayer piezoelectric transformer(MPT) has been proposed based on the Mason's equivalent circuit model and the principle of single layer piezoelectric plate. From the piezoelectric direct and converse effects, the symbolic expressions between the electric inputs and outputs of the MPT have been derived from the equivalent circuit model. A simplified equivalent circuit model of the MPT whose driving part has a single input form has been proposed. The symbolic expressions of the driving part have been derived from the simplified equivalent circuit model and the model was compared with the multi-input equivalent circuit model through the simulation. In the comparisons between the simulation results and the experimental data, output voltage is 630 Vp-p in case of 11-layered MPT and 670 Vp-p for 13-layered MPT over the experiment range. As the load resistance increases, output voltage increases and saturates over $300k{\Omega}$ and the resonant frequency changes from 102 kHz to 103 kHz. The simulation and the experimental results agree well over different load resistances and frequencies.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1355-1361
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• 2016

The inter-turn fault (ITF) causes the negative sequence components in the d -q voltage equation due to an increase in the unbalance of three-phase input currents. For this reason, d -q voltage equation become complicate as the voltage equation is classified into positive and negative components. In this study, we propose a simplified d -q equivalent circuit of an interior permanent magnet synchronous motor under ITF state. First, we proposed modeling method for d -q current based on the finite element method simulation results. Then, we developed the simplified d -q equivalent circuit by applying the proposed d -q current modeling.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9A
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• pp.1434-1441
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• 1999

This paper presents an equivalent circuit of the hairpin line filter for accurate analysis and design. Its validity was verified by computer simulations and filter design experiments. Though the various design equations for a hairpin line filter have been proposed, there has not been a practically simplified equivalent circuit because it is hard to effectively represent interconnection effects between non-adjacent elements. In this paper, all the open ports of the hairpin line filter circuit are changed to the short ports using circuit duality, and the resulting circuits are transformed to graph model. The further simplified circuit model is obtained from boundary conditions, and then the final equivalent circuit of the hairpin line filter is derived in a dual structure of the filter.

• Journal of Power Electronics
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• v.18 no.3
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• pp.902-909
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• 2018

This study investigates the influences of different core parameters on the dynamic performances, such as rise time and overshoot, in pulse transformers for the triggering circuit of SCRs. First, a simplified transformer equivalent circuit, which emerges from a standard transformer equivalent circuit, is developed to analyze the step response. Second, the relations between the dynamic performances and the parasitic parameters are calculated by the simplified equivalent circuit. Third, the variations of rise time and overshoot, which are vital to the stability of triggering SCRs, with different core parameters, such as mechanic dimensions and topologies, are comprehensively investigated by analyzing the parasitic parameters. Finally, prototype transformers are fabricated to experimentally validate the analysis. The presented method can practically instruct the design of a pulse transformer for triggering SCRs.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.236-240
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• 1988

The simplified equivalent by using the short circuit impedance has been used for analyzing the prospective transient recovery voltage of the large power system. But it sometimes generates untorelable error in the rate-of-rise of TRV when using the Thevenin equivalent source. This paper provides the new equivalent by using the multi-port theory. The application of the new method to the sample system gives satisfactory accuracy compared with the short-circuit equivalent.

• Journal of Advanced Marine Engineering and Technology
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• v.9 no.1
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• pp.61-73
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• 1985

The induction motor is widely used in the power equipments of the ship and the various industrial drive applications because it is robust and relatively simple and cheap to manufacture, but it has a disadvantage that the speed of induction motor is not controlled in wide range such as d.c motor. In this paper, the characteristics relating to the Kramer system that the speed of three phase wound type induction motor is controlled by changing the exciting e.m.f. of the secondary circuit is described. In order to analyze the characteristics, a new simplified and approximated T-type equivalent circuit from the Kramer circuit with three phase graetz connection and d.c machine is proposed. The stator current, motor torque and mechanical output power are computed by the current, torque and power equations derived by its equivalent circuit. Through the experiments, the $I_f-N$, torque-slip and current-slip characteristic curves of the tested motor are obtained and the various needed constants are determined. The numerical values obtained from the above method are compared with experimental values under the same conditions. As a result of the above investigation, it is found that the induction motor speed by the Kramer system is controlled by 28 per cent under the rated speed by changing the field current of d.c motor and the values computed by the current and torque equations derived by the simplified and approximated T-type equivalent circuit generally come to approach the experimental values.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.3
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• pp.174-181
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• 2018

This study introduces a systematic approach to selecting the internal parameters applied to the equivalent electrical-circuit model (EECM) of a lithium titanium oxide ($Li_4Ti_5O_{12}$; LTO) rechargeable cell. Based on the dynamic characteristic of the cell, a simplified EECM consisting of an open-circuit voltage (OCV), an ohmic resistance, and an RC ladder is fabricated. To select the internal parameters of a simplified EECM, experiments on discharge capacity, OCV, and discharge/charge resistances are performed using hybrid pulse power characterization and direct current internal resistance (DCIR) measurements over the full state-of-charge (SOC) range. The experimental results of the LTO rechargeable cell highlight the importance of correct selection of internal parameters that can reduce EECM errors. This study clearly provides experimental procedures, internal parameters results, and EECM guidelines for adaptive control-based SOC estimation for LTO rechargeable cells.

• Transactions on Electrical and Electronic Materials
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• v.17 no.1
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• pp.13-17
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• 2016

The ampere-hour integral method and the open circuit voltage method are integrated via the extended Kalman filter method so as to overcome insufficiencies of the ampere-hour integral method and the open circuit voltage method for estimating battery SOC. The process noise covariance and the measurement noise covariance of the extended Kalman filter method are simplified based on the Thevenin equivalent circuit model, with a proposed simplified SOC estimating method. Verification of DST experiments indicated that the battery SOC estimating method is simple and feasible, and the estimated SOC error is no larger than 2%.