bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electric citybus with two induction motors ‐power electronics and motor control
Authors: Langheim J. , Fetz J. 
Published: July 2010

AbstractAfter a short introduction into the project of an electrically driven citybus with two individual induction machines, this paper describes the power electronic hardware including IGBT‐inverter and on‐board supply system as well as the structure of the field‐oriented motor control. The on‐board power supply has been especially designed for this vehicle. It supplies electric loads such as board systems, measurement devices and control components. The induction machines are separately fed by two ICBT‐inverters. They are operated at a high switching frequency due to the low leakage inductance of the machines. Fast switching leads to high dU/dt‐values which may destroy the motor windings. In order to reduce the high dU/dt‐stress on the machines, an appropriate circuit has been developed and is presented. The induction machines are controlled by a field oriented control. The choice of the reference current components and the control structure assure a good dynamic performance and low machine losses. Measurements obtained in a laboratory test‐setup are presented.
Piezoelectric motors and their applications
Authors: Schöner H.‐P. 
Published: July 2010

AbstractThe principle of operation of piezoelectric motors is explained. Different general approaches for converting small displacements of the piezo element into continuous motion are described. The use of resonant oscillations gives relatively powerful piezoelectric motors. A short review of the historical development is given. General properties of piezoelectric motors are explained. Limiting factors for the power of piezoelectric motors are discussed in comparison to standard electromagnetic motors. The force per active area of piezoelectric motors is shown to be 30 to 100 times larger compared to small electromagnetic motors. The tilted speed/torque characteristic is explained from material properties in the motor. Other general aspects, especially with respect to the choice of materials, are discussed. This motor type will provide advantageous solutions especially for many different positioning applications.
Calculations of resistances and reactances of a single‐sided linear induction motor
Authors: Gieras J. 
Published: July 2010

AbstractThe equations for resistances and reactances of the equivalent circuit of a single‐sided linear induction motor with a double‐layer reaction rail (secondary) are given. The influence of the magnetic saturation due to leakage fluxes on the primary winding leakage reactance and the influence of the longitudinal end effect on the vertical branch impedance is discussed. Other effects such as the transverse edge effect, the skin effect, the non‐linearity of magnetic circuit and the primary compensating turns are also included. It is proved that the equivalent circuit gives a better accuracy than the finite element method in case of calculating the thrust and normal force of a large‐scale linear induction motor.
Contribution to the calculation of electromagnetic channels for molten metal transportation
Authors: Pesteanu O. 
Published: July 2010

AbstractThe paper presents the construction of a conveying channel of relatively small active power and with direct network supply of the inductor winding. By calculation of the magnetic field with the variables‐separation method, on one side, and by representation of the conveying channel as a cascade of four‐terminal networks on the other, an equivalent circuit is determined, which takes into consideration the following: the reaction of currents induced in the molten metal, in the protective plate and in the cooling tubes of the inductor, the transverse edge effects, the magnetic field decrease normally to the inductor surface, the influence of slot openings and the higher waves of the travelling magnetic field. Finally two industrial dosing channels are presented.
Apparent and reactive powers in three‐phase systems: In search of a physical meaning and a better resolution
Authors: Emanuel A. E. 
Published: July 2010

AbstractThis work analyzes the resolution of the apparent power in three‐phase systems defined by means of symmetrical components and using the product between an equivalent voltage [(V+)2+(V‐)2+(V0)2]1/2 and an equivalent current [(I+)2 + (I‐)2 + (I0)2]1/2. It was found that each component of such a defined apparent power S has a definite physical meaning. The results emphasize the need to separate the negative and zero sequence active power from the positive sequence power.
Current and power equations at bidirectional flow of harmonic active power in circuits with rotating machines
Authors: Czarnecki L. S. 
Published: July 2010

AbstractA substantial portion of electric energy, up to two third of the amount produced, is converted into mechanical energy by various rotating machines. These are supplied mainly from three‐phase sources of a sinusoidal voltage. There are situations, however, where this voltage is strongly distorted. In recent years, progress was achieved regarding comprehension of the power phenomena in circuits with non‐sinusoidal voltages and their power factor improvement. This is due to a power theory based on the current orthogonal decomposition into the active, scattered, reactive and unbalanced current. That theory does not take into account, however, peculiar power properties of the rotating machines. This paper suggests a modification of this theory to a form that might be more suitable for describing the flow of energy between a rotating machine and a three‐phase source of non‐sinusoidal voltage.
A kalman filter‐based technique for combined digital estimation of voltage flicker and phasor in power distribution systems
Authors: Kamwa I. , Srinivasan K. 
Published: July 2010

AbstractElectric power quality is of prime importance when sensitive electronic equipment is involved. One of the aspects of power quality is known as flicker level. The present paper proposes an algorithm for real‐time monitoring of voltage flicker based on the Kalman filtering technique. First a stochastic state space model of the system voltage with a linear time‐invariant transition matrix has been established, yet non‐linear in the scalar observation model. Using noisy measurements of a single‐phase voltage, an extended Kalman filter leads to instantaneous value of rms voltage and phase. Then the flicker level has been derived by appropriate filtering and statistical processing on short records of the rms voltage measurements. Simulated and actual data demonstrating the effectiveness of the overall scheme in estimating voltage phasor and flicker for a wide range of swing frequencies are presented and discussed. Among the several power system applications of the new stochastic observer considered, a remote load control concept based on the carrier amplitude modulation is shown being possible and included are test results confirming the filter capability to retrieve sequences of amplitude‐modulated bit patterns travelling through the power line to customer sites.
Microprocessor‐based speed control of DC motor fed from semiconverter supply
Authors: Zaki A. M. , El‐Sattar A. A. , Wahsh S. , Amer S. 
Published: July 2010

AbstractThe tremendous progress in semiconductor technology has made solid state DC motor drives suitable for many practical applications. In this work a simple method for gate control of a semiconverter circuit feeding a separately excited DC motor is presented which is used to vary the motor speed. The transient as well as steady‐state characteristic performances have been obtained theoretically using closed form solution and experimentally using digital techniques. The required firing pulses were generated digitally using a 16‐bit microprocessor system. A set‐up for the experimental system has been designed and built in the laboratory. There is excellent agreement between the computed results and those obtained from the actual set‐up.
Numerical simulation of induction heating: A finite‐element approximation
Authors: Conraths H.‐J. 
Published: July 2010

AbstractA precise knowledge about the electromagnetic field, the eddy currents and the temperature distribution is necessary to optimize induction heating devices which are used to heat up thin, moving metal strips in a continuous process. As this information cannot be gained from conventional, analytical methods, a new numerical simulation method, based on a finite‐element approximation, has been developed. The coupled electrical‐thermal process is modelled by a set of partial differential equations which are discretized using the Method of Weighted Residuals (Galerkin‐Method). The temperature dependency of the electrical and thermal conductivity as well as convection and radiation at the surface of the strip are included in the mathematical model. The validity of this numerical approximation is proved by the comparison of calculated and measured temperature distributions in two test cases. Finally, a simple example shows how the new method can be used in the analysis and optimization of the induction heating system.
Short‐term load forecast by plausibility checking of announced demand: An expert‐system approach
Authors: Markovié M. L. , Fraissler W. F. 
Published: July 2010

AbstractShort‐Term Load Forecast at Verbundgesellschaft (VG ‐ the Austrian Electricity Board) is presented. As the VG has only regional utilities and large industries as purchasers, classical forecast methods are not appropriate. Much more suitable is a plausibility check of a set of announced purchasers demands, for which an expert system has been developed for one to three days ahead forecasts. It has been realized with the help of a rule‐oriented expert system shell based on Prolog, and contains about 250 rules. Normal days as well as special days are considered. The prototype has been tested at the central dispatcher of the VG since autumn 1990. Results and acceptance by the users are promising.
Apparent power and power factor definitions for polyphase non‐linear loads when supply conductors present different resistances
Authors: Mayordomo J. G. , Usaola J. 
Published: July 2010

AbstractA time‐domain based method of defining the apparent power is presented. It is a generalization of the De‐penbrock method to systems whose supply conductors have different resistances. The so defined apparent power can be split into orthogonal components and it is coherent with the physical meaning of the power factor.
AC/DC current source GTO converter with high power factor
Authors: Alexa D. , Pastravanu A. 
Published: July 2010

AbstractThe paper proposes a new pulse‐width‐modulation controlled AC/DC current source GTO converter circuit. The circuit operation and its performances are investigated. This converter has low harmonic content and does not require any reactive power from the AC power source. An active power filter with capacitive and inductive storage is used for these purposes. A linear variation and a wide control range of the DC output voltage of the converter versus relative connecting duration are also obtained. Such a converter can be efficiently used to get a static frequency converter with direct current link, which can drive an induction motor with adjustable voltage and frequency.
Current chopping phenomena in SF6 selfblast circuit breakers
Authors: Voigt G. 
Published: July 2010

AbstractIn SF6 selfblast circuit breakers the arc energy provides a current dependent pressure rise in the upstream volume. For successful interruptions for smaller currents a current independent gas flow is necessary. The gas flow can cause current chopping when small inductive currents are interrupted. In the present paper chopping phenomena are investigated experimentally. Arc time constants are determined by current step experiments. A two‐pole arc model is used for the simulation of the observed phenomena.
Robust excitation controller design for synchronous generators using output feedback
Authors: Papadopoulos D. P. , Bandekas D. V. , Smith J. R. 
Published: July 2010

AbstractIn this work an alternate systematic procedure is proposed for the control of high‐order multiple‐input multiple‐output (MIMO) linear time‐invariant open‐loop system models. The procedure forms the corresponding high‐order single‐input multiple‐output (SIMO) open‐loop model from which it obtains an adequate reduced‐order SIMO open‐loop model (all states of which are measurable and may be made to coincide with its output variables). Then an implementable controller based on the reduced‐order SIMO model, using the spectral pole‐placing algebraic control method with complete state‐feedback, is derived. The controller of the reduced‐order SIMO model is then used for controlling the original high‐order MIMO open‐loop system model. The proposed control approach was applied to a linearized 9th‐order MIMO open‐loop synchronous generator system model and yielded an implementable excitation controller, which was tested successfully in three more operating points of the over‐ and under‐excitation regions of the generator for proving its desired robustness. The four designed 9th‐order MIMO closed‐loop systems displayed remarkably improved dynamic stability characteristics.
Measuring differential inductances of asynchronous machines
Authors: Staudt V. 
Published: July 2010

AbstractAsynchronous machines in traction applications are normally saturated during voltage‐controlled operation. The saturation has an influence on the differential inductances of the stator windings. The value of these differential inductances can be calculated based on a theory and measured during a pulse period of the feeding voltage‐source inverter (VSI). This paper concentrates on the measurement of differential inductances and contains only a short recapitulation of the theory. Measured values of differential inductances might be used to estimate the stator‐flux space vector of the asynchronous machine without speed measurement even at stator frequency zero as a basis for high‐performance torque control without speed measurement.
On the electrical behaviour of the polar liquid propylene carbonate: a pseudo‐ohmic current‐voltage relation
Authors: Dittrich W. 
Published: July 2010

AbstractPropylene carbonate (PC) is a liquid with significant dissociation ofionizable molecules. The dissociation velocity is nearly proportional to the field strength. By this the electric current becomes almost proportional to the field strength resulting in a pseudo‐ohmic current‐voltage relation. A model is presented, which allows an interpretation of the experimental current‐time and current‐voltage dependence.
A new family of electrical insulating fluids: perfluorinated polyethers
Authors: Pompili M. , Mazzetti C. , Forster E. O. 
Published: July 2010

AbstractPerfluorinated hydrocarbons, because of their chemical inertness and thermal stability, have been used for a number of years in a limited number of applications in the electrical and electronic industries. Recently, a new family of perfluorinated ethers has become commercially available. Physical properties of this new family of insulating fluids include non‐flammability, high density and a wide range of viscosities. The physical and electrical properties of two representative samples of this family have been studied in detail and compared with those of other insulating oils. The results of this study suggest that these fluids should be of considerable interest to the electrical industry, particularly in applications requiring a high degree of fire protection combined with environmental compatibility.
The mean generalized content: a conservative quantity in periodically‐forced non‐linear networks
Authors: Superti Furga G. , Pinola L. 
Published: July 2010

AbstractNon‐linear networks working in periodical non‐ sinusoidal steady state are investigated. By means of a new balanced quantity, theorems and conditions are achieved about some aspects in the harmonic generation and in the power conversion at different frequencies. An extension of the concept of reactive power emerges too. A numerical example is discussed in details and relevant results are reported.
The iec 909 standard and dynamic simulation of short‐circuit currents
Authors: Castelli‐Dezza F. , Silvestri A. , Zaninelli D. 
Published: July 2010

AbstractIt has taken a very long time for the Standard Committees, the VDE followed by the IEC, to complete their work on a standard for the unambiguous and conventionally correct determination of the characteristic values which identify the short‐circuit current in low‐medium and high‐voltage systems. This history forms one of the reasons why the procedure employed in the IEC 909 standard, finally arrived at, is potentially oriented towards manual implementation. This procedure is based on an approximation to the method of superposition of the effects; this approximation, however, gives sufficiently accurate results thanks to the use of a number of correction factors, mainly experimental in origin. The present‐day availability of reliable and reasonably priced calculation software for the study of the dynamic behaviour of electric energy systems has suggested a comparison between the results of calculations in accordance with IEC 909 and those using a dynamic simulation dealt with under the well‐known code EMTP. The test networks chosen are precisely those (in increasing order of completeness) put forward and resolved in Appendix A to the IEC 909 standard. The comparison shows a good measure of agreement between the two methods, permitting comment on ‐ and discussion of‐ the two approaches.
Equivalent circuit for small solid‐rotor induction motors fed from a non‐sinusoidal supply
Authors: Abdel‐Halim I. A. M. , Mansour H. A. , El‐Kassas S. I. , Hamed H. G. 
Published: July 2010

AbstractIn this paper an equivalent circuit for small solid‐rotor induction motors is developed in which the effect of the time harmonics of the supply are taken into consideration when the supply is non‐sinusoidal. This circuit can be used to obtain directly the characteristics of the motor, such as torque speed, current speed etc., when the motor is fed from a non‐sinusoidal supply, in the same way as the characteristics of the cage motor are obtained.
Time‐frequency representations of instantaneous complex power, voltage and current space vectors
Authors: Salvatore L. , Savino M. 
Published: July 2010

AbstractThis paper introduces a new time‐frequency representation and analyses the time‐frequency structure of the instantaneous complex power, voltage and current space vectors, which are powerful mathematical tools to describe the behaviour of three‐phase systems under unbalanced and non‐sinusoidal conditions. Computer simulations are carried out so that the performance of the new time‐frequency representation can be verified.
Comments on “apparent and reactive powers in three‐phase systems: in search of a physical meaning and a better resolution”
Authors: Czarnecki L. S. 
Published: July 2010

AbstractIt is shown in this comment that it is not so obvious that the apparent power S “has a clear physical meaning “ as it is asserted in the paper “Apparent and Reactive Powers in Three‐Phase Systems: In Search of a Physical Meaning and a Better Resolution “ published by A. E. Emanuel in ETEP 3 (J993) no. I. Moreover, the author of the discussed paper misinterprets power properties of unbalanced systems. He asserts in Section 2 that, apart from the active power P, each power in systems with sinusoidal waveforms represents the amplitude of an oscillation of power. The apparent power S in unbalanced systems may be higher than the active power P, however, despite of the lack of any oscillation of instantaneous power, since the direction of energy flow may not change with the load unbalance. The unbalanced power of a resistive unbalanced load cannot occur as a consequence of power oscillation since such a load does not have any capability of energy storage.
Steady‐state analysis of three‐phase self‐excited reluctance generators
Authors: Alolah A. I. 
Published: July 2010

AbstractA three‐phase reluctance machine can be made to operate as a self‐excited generator when its rotor is driven at suitable speed by an external prime mover and its excitation is provided by a capacitor bank connected to the stator terminals. The reluctance generator has almost all the advantages of its counterpart induction generator and has in addition the advantages of constant frequency operation and low core and copper losses. This paper introduces an analysis of the three‐phase self‐excited reluctance generator. The developed analysis avoids the limitations of the previous works whereby the effect of the core loss is soundly taken into consideration. The analysis is suitable for variable speed, load and excitation capacitance operations. The validity of the proposed analysis is confirmed experimentally. The effect of neglecting the core loss is also studied.
Method for distance estimation of single‐phase‐to‐ground faults in electrical distribution networks with an isolated or compensated neutral
Authors: Lehtonen M. 
Published: July 2010

AbstractThe paper discusses how current and voltage measurements derived from the substation can be used for single‐phase‐to‐ground fault location in medium‐voltage distribution lines. The networks considered are assumed to be radially operated with either an isolated or compensated neutral. In these networks the fundamental frequency ground fault currents usually are so small that no reasonable fault‐distance estimate can be based on them. A possible solution is the utilisation of ground‐fault initial transients. In this paper a method for ground‐fault distance estimation, based on the least squares estimation of transient parameters, is presented.
Effect of machine and balancer parameters on the pulling into step of three‐phase reluctance
Authors: Alolah A. I. , Alsalloum A. M. , Badr M. A. 
Published: July 2010

AbstractThe operation of three‐phase reluctance motors when fed from a single‐phase supply has been found possible through the use of an appropriate capacitor as a phase balancer. This adds more flexibility to the modes of operation of such motors. Analysis of the associated transient process of this mode of operation has not yet been dealt with in the literature. It is the main objective of this paper to present a rigorous analysis of the transient behaviour of the three‐phase reluctance motors fed from a single‐phase supply. Particular attention will be focused on the pulling‐into‐step problem as affected by different motor‐ and supply‐system parameters. The developed mathematical model is suitable also for analysing the transient behaviour of three‐phase reluctance motors under balanced operating conditions.
A knowledge‐based method for contingency evaluation
Authors: Yerima J. Y. 
Published: July 2010

AbstractIn this paper new algorithms for contingency evaluation and a test of their validity with respect to accuracy are presented. These algorithms are based on a quantitative knowledge established for an arbitrary network operating state. The knowledge base is acquired by quantifying the impact of all single‐branch outages on the voltage and current profile using AC load‐flow‐based techniques. The acquired knowledge base can be utilized together with the derived formulae to evaluate the impact of multiple‐branch outages. Based on these formulae a technique has been proposed for updating the knowledge base to reflect changes in network topology. The knowledge‐base updating technique is efficient and the computational requirements are small. By defining a branch‐outage dependency factor an approach is presented to quantify the accuracy level of the results of multiple‐branch outages and to identify multiple‐branch outages leading to large computational errors. Generation unit failures are modelled using branch outages.