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A modified pi-shaped circuit-based model of grounding electrodes
(2016-12-19)
Yutthagowith, P.
This paper proposes a modified pi-shaped circuitbased model of grounding electrodes. The validity length and soil resistivity of the proposed model are from 2 m to 40 m and from 50 m to 2000 m, respectively. The equivalent circuits in the form of pi configuration are modeled by lumped parameters composing of inductance, resistances, and capacitances. The voltage responses to the standard lightning currents of grounding electrodes either calculated by an electromagnetic model or from experiments are matched with those of the proposed model. A curve fitting technique is employed to extract parameters of the equivalent circuit. The satisfactory agreements have been observed. The simple soil ionization model can readily be adapted in the proposed model. The proposed model is very useful in implementation with a circuit simulator such as EMTP, Pspice, and so on. The proposed circuit model can be adapted for being the models for development and design of the grounding system for lightning protection system in transmission and distribution systems in an effective way.
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Low-intrusive approach for parameters estimation of induction motor using adaptive optimal design algorithm based on on-site measurements
(2013-01-01)
Chat-Uthai, C.
;
Phumiphak, P.
This paper presents a novel low-intrusive method for estimating the equivalent circuit parameters of induction motor which focuses on a simple means without expensive testing. This paper describes the use of on-site measurements data incorporated with the adaptive optimal design algorithm based on optimization process in order to estimate the best possible set of motor parameters for determining the mechanical output at each measured load. This algorithm includes the feasible boundary of design variables process for evaluating the suitable boundaries of motor parameters depending on its power rating. This proposed method has been verified by the experimental results from four low-voltage TEFC induction motors rated at 2. 2, 4. 0, 5. 5 and 7. 5 kW. The results indicate that the agreement between the estimated parameters and the calculated parameters obtained from the standard equivalent circuit method validates the proposed method over a wide range of load conditions. For comparison, the results of estimated mechanical output of actual motors are illustrated. Therefore, this simple procedure can provide the useful information for selecting the motor most suitable for its application. © 2013 Praise Worthy Prize S.r.l.-All rights reserved.
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Internal failure analysis of transformer windings
(2012-12-31)
Tuethong, P.
;
Yutthagowith, P.
;
Kunakorn, A.
;
Potivejkul, S.
This paper presents internal failure analysis of transformer windings based on the characteristic of winding impedance in the frequency domain. Two winding samples are selected to test. The simple equivalent circuit of the transformer winding is investigated and proposed. The two windings under test have 76 turns with different length. An iron core is either inserted or not inserted inside a winding in the test to investigate the effect of the iron core. Turn to turn short circuit on the windings is considered as internal failure in this paper. The simulated turn to turn short on the model is carried out in the experiment to observe impedance characteristic in the frequency domain. A number and position of short turns are varied to observe characteristics of impedances The impedance of the models of the transformer windings are measured by a spectrum analyzer in a wide frequency range upto 2 MHz. From the test results, it is investigated that a resonance frequency of the transformer model is depended on a number and position of short turns. From the investigation, it has high possibility that the characteristic can be used for analysis of internal failures occurring in a transformer. © 2012 IEEE.
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Electrical equivalent circuit model and impedance of Euglena sanguinea stimulated by multi-level electromagnetic fields
(2010-10-11)
Packamwongsang, Komphet
;
Noppanakeepong, Suthichai
This research studied the characteristic of electrical properties of E. sanguinea by evaluation of complex impedance and complex permittivity. Apply Cole-Cole plot technique to explain the behavior of RC impedance form simulation and measurement. The objective of this study was to build up a new electrical equivalent circuit model from RC circuit model of E. sanguinea with MLEMF. The results revealed that there were a correlation between impedance from measurement and simulation with correlation value equal to 0.83 at 95% confidence interval. The RC impedance of E. sanguinea of each chemical component, i.e., protein, chlorophyll, carbohydrate, lipid and phosphorus was behavioral in semicircle varied to frequency which give the correlation with complex permittivity. The model can be used for design of water supply system by MLEMF for treating algae bloom water. This is an innovative electric simulation applicable to the electric engineering and other related fields of study. © 2010 IEEE.
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Optimal capacitances compensation for short-shunt self-excited induction generator under inductive load
(2009-12-01)
Phumiphak, P.
;
Chat-uthai, C.
This paper presents a technique for evaluating the optimal values of capacitances necessary to maintain the power quality of voltage regulation of the short-shunt self-excited induction generator (SEIG) feeding to the desired pu load under various lagging power factor conditions. The optimal values of shunt and series capacitances, and the optimal relation of ratio of air gap voltage to frequency with magnetizing reactance for the minimum voltage regulation of SEIG are evaluated by using the technique of genetic algorithm (GA) based on the equivalent circuit parameters of machine. Experimental results of 0.75 kW, short-shunt SEIG are performed to confirm the effectiveness of this proposed technique. The results are experimentally verified, which illustrate that the voltage regulations of SEIG under different inductive loads are within the limit of ± 0.06 pu.
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An economical method for induction motor field efficiency estimation for use in on-site energy audit and management
(2004-12-01)
Phumiphak, Thanaphiwat
;
Chat-uthai, Chaiwut
This paper proposes an economical method that can help the plants to make right decision in replacing the inefficient induction motors with more efficient ones. This method focuses on the field efficiency of motors without the needs for removing motors and measuring the output power. The use of a few sets of measured data from field test coupled with the genetic algorithms for evaluating motor equivalent circuit instead of using the no-load and blocked-rotor tests is proposed. To illustrate how well the estimated efficiency matches that of calculated obtained from the standard evaluations, the results of various induction motors rating up to 100 hp are presented. Test results indicate that this method has a high accuracy, then it is suitable for conducting on-site energy audits of motors in order to project cost savings and payback and to support a confidence decision regarding the investment in higher efficiency motors. © 2004 IEEE.

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