bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensorless control of permanent‐magnet synchronous machines at arbitrary operating points using a modified “inform” flux model
Authors: Schrödl M. 
Published: July 2010

AbstractA new method based on the “Inform” principle is presented enabling control of permanent‐magnet synchronous motors without speed‐ and position sensors. A special measurement procedure detects the electrical rotor angular position by using test signals generated by the inverter. The basic idea is to measure the different inductances in direct and quadrature axis due to saturation effects or construction. The sign of the magnetic flux is detected by shifting the magnetic set‐point with a certain armature current. Some possibilities of how to calculate the rotor angular position from test signals are given. Measurements using a DSP‐controlled drive verify the practical applicability of the new principle.
Contraction of bundled conductors in outdoor substations determined by the parabola model
Authors: Zeitler E. 
Published: July 2010

AbstractBundled conductors in outdoor substations contract in case of a short‐circuit. These cause a marked peak value of the tensile force, the so‐called pinch force, which may be crucial to the dimensioning of a substation. A reasonably simple, and at the same time sufficiently exact method for the calculation of the pinch force is the presented Parabola Model.
Calculation of three‐dimensional magnetic field for horseshoe electrode of vacuum interrupters
Authors: Schellekens H. , Shang W. , Lenstra K. 
Published: July 2010

AbstractIn this paper, the integral equation method for static magnetic fields has been implemented for a three‐dimensional (3D) problem with given current distribution and geometry of different materials. These methods are suitable for general 3D magnetic field problems. The algorithms are given to calculate the 3D magnetic field of horseshoe electrode of vacuum interrupters. Examples of calculated results of axial magnetic fields are given.
On the performance of spacer dampers in bundled conductors
Authors: Hagedorn P. , Kraus M. 
Published: July 2010

AbstractIn bundled conductors of overhead transmission lines spacers are used to maintain the distance between the individual conductor cables. These spacers are often provided with elastic and damping properties with the intent to damp out the mechanical vibrations due to vortex shedding in the frequency range between 10 Hz and 60 Hz. The present paper deals with a simple mechanical model of spacer dampers, which permits the study of the influence of different mechanical parameters on their damping performance. The dynamical characteristics of industrial spacer dampers determined in laboratory experiments can thus be compared to the values which are optimal from the vibrations damping point of view.
Research on the breakdown under type test of non‐pressurized paper‐insulated HVDC cables
Authors: Priaroggia P. Gazzana , Metra P. , Miramonti G. 
Published: July 2010

AbstractOne of the most interesting and important problems, met during the development of non‐pressurized impregnated paper cables for high voltage direct current, arose from the introduction of a long‐duration type test at thermal cycles under a DC steady voltage of twice the working voltage. DC cables manufactured according to a traditional paper insulating technique showed during the cooling phase of a thermal cycle a catastrophic fall of the dielectric strength of the order of 50 %. The reason for this fall is analysed both theoretically and experimentally and the way to overcome the obstacle is explained and discussed.
Asynchronous motor cage fault detection through electromagnetic torque measurement
Authors: Thollon F. , Grellet G. , Jammal A. 
Published: July 2010

AbstractIn this article a new method is presented allowing the diagnostic of bar or ring rupture of a cage of asynchronous machine. It is shown that a modelling of the asynchronous machine taking into account each bar and each portion of ring of the cage allows to consider the influence of a rupture upon the expression to the instantaneous electromagnetic torque. It has been put up an instrumentation permitting the measurement of this torque. The spectral analysis of the parameter leads to the diagnostic of a cage rupture by discriminating this fault from other faults, particularly mechanical ones. It is also observed that ruptures influence greatly the electromagnetic torque. The peak variation of the significant spectral lines is so important that it allows the detection of a first rupture without the need of a very sophisticated instrumentation.
Examination of transient phenomena in induction machines, caused by an incorrectly adjusted rotor‐time constant in a field‐orientated control system
Authors: Rapp H. 
Published: July 2010

AbstractField‐orientated control systems for induction machines are very sensitive to variations of the machine's rotor‐time constant. This paper deals with the transient phenomena occurring after each change of the machines load, if the rotor‐time constant is not adjusted correctly. After an analysis of the transient phenomena being in question, measures for diminishing them are discussed.
Inverter motor with sinusoidal starting currents ‐ a survey
Authors: Möhlenkamp G. 
Published: July 2010

AbstractInverter motors need only simple line‐ and machine‐commutated converters and have proved good performance for drives in the MW range. They cause high torque ripple, which is disturbing only at low frequencies, and require additional commutation devices under heavy start‐up conditions. The also very economic cyclo‐converters are only useful for machine frequencies up to about 40 % of line frequency. The new systems proposed here combine the advantages of both drives with two DC links only. The same circuits operate as a cy‐cloconverter at start‐up and low frequencies of the motor, and as a current‐source inverter at high speeds. The switchover possibilities from one operation mode to the other without any transient reaction are shown. The necessary expenditure compared to the conventional inverter motor is presented.
Skew leakage in induction machines
Authors: De Jong H. C. J. 
Published: July 2010

AbstractMost induction motors have their rotor slots skewed, i. e. twisted away from the axial direction, with the intention to reduce harmful slot harmonic effects. As skewing affects the magnetic coupling between primary and secondary windings, also the fundamental harmonic performance is involved. The latter effect can be expressed for the wound‐rotor type by various modifications of the equivalent circuit, each of which corresponds with a pair of imaginary reference windings. The scaling law of the skew leakage reactance is discussed and compared with the scaling laws of the other leakage reactance components. For cage induction machines, special attention is paid to the omission of rotor bar insulation, its connection with the capricious character of skew leakage and its representation in the equivalent circuit.
Verification of the electromechanical transients program setpos by means of comprehensive power‐station measurements
Authors: Lund P. 
Published: July 2010

AbstractMost electrical power engineers involved with the planning and designing of power station auxiliary power supply systems are faced with the problem of credibility of the electromechanical transients programs offered as supplementary aid in fulfilling their jobs. These programs contain a variety of mathematical models of electrical power system components, which can be combined to constitute the electrical system being analysed. Most simulation programs have been tested on a number of theoretical cases and the results compared to those of other similar computer programs. This is due to the general lack of‐ and difficulties in achieving ‐ field measurements of reproducible electromechanical transients in fully known power subsystems. Such field measurements of a slow busbar switching in the auxiliary system of a modern power station unit are presented and compared to the computational results obtained by simulating the incident using the SETPOS electromechanical transients program.
The use of decentralized measures of mobility of modes for feedback signal selection and optimum siting of power system stabilizers
Authors: Hamdan H. M. A. , Hamdan A. M. A. 
Published: July 2010

AbstractThe problem of choosing an optimum site for the power system stabilizer in a multimachine power system (MMPS) is considered. The method used is based on the concept of mobility of modes in a decentralized control system. The singular value decomposition of appropriate matrices is used as a computational tool. The minimum singular value of appropriate matrices is used as an index of controllability and observability of a given mode. The method takes into consideration the input and output matrices of the linearized state space models of MMPS. This is an advantage over methods that are based on the state matrix only. This advantage makes it possible to evaluate more signals in one site than is possible through previous methods. Two examples are used to demonstrate the effectiveness of the method.
A new approach to high‐power arc dynamics
Authors: Schötzau H. J. , Kneubühl F. K. 
Published: July 2010

AbstractUp to the present the Mayr equation has been used for studies of the interaction of high‐power arcs with electrical networks. In the present study the Mayr equation is generalized with the aid of response and relaxation functions. It is demonstrated that this concept reaches far beyond the Mayr equation. Thus, the problem of small inductive currents in LCR circuits including an arc is solved comprehensively. In this context, the influence of a delayed arc response is revealed and new effects are predicted.
Generation of uncharacteristic harmonics in electrical plants with ac/dc converters
Authors: Loggini M. , Montanari G. C. , Cavallini A. 
Published: July 2010

AbstractIn this paper an investigation is carried out on the correlation between dissymmetry imbalances and the generation of uncharacteristic harmonics in low‐voltage electrical plants supplying A C/DC six‐pulse converters. After a general introduction, some typical cases of dissymmetries and imbalances are considered, relevant to supply voltage, line impedances, thyristor injection angles and filter capacitors, and the corresponding uncharacteristic harmonic currents derived by means of the simulation program EMTP. Moreover, evaluation of harmonics is made for various values of plant and load parameters in order to derive the behaviour of amplitude and phase of uncharacteristic harmonics in a wide range of plant conditions. The results provide clear relationship between kind and degree of dissymmetry and presence of uncharacteristic harmonics with useful indications for plant design.
Dynamic, power‐quality‐oriented approach to power theory and compensation of asymmetrical systems under non‐sinusoidal conditions
Authors: Czarnecki L. S. 
Published: July 2010

AbstractCurrent and power equations of three‐phase circuits with unbalanced non‐linear loads supplied from asymmetrical and non‐sinusoidal voltage source are developed in the paper. It is suggested that the form of the power equations should be adjusted to the goal for which they are developed. Their form, which may be convenient for interpretation of power phenomena, may therefore differ from the one developed for studies on the supply and loading quality. Also it is shown that power properties of a circuit cannot be wholly determined in its static state. They can be determined, however, if the circuit response to the supply changes is observed. Such an observation and analysis of the circuit response are considered as a dynamic approach. It may provide a control algorithm for adaptive compensators.
Dynamic compensation of non‐active power using the fbd method ‐ basic properties demonstrated by benchmark examples
Authors: Depenbrock M. , Skudelny† H.‐Ch. 
Published: July 2010

AbstractFor the most general case of electrical polyphase circuits under non‐sinusoidal, unbalanced but steady‐state working conditions there are different definitions of active quantities needed for power transfer and non‐active quantities which could be compensated without changing the average power transfer. In practice normally the load is varying with time, therefore it is interesting how the definitions of power quantities can be extended to dynamic working conditions and what are the results of compensating non‐active quantities in such cases. Even if the load does not change with time after the start of a controllable compensator, the complete system is time varying. For this case it is shown how the non‐active quantities as defined within the FBD Method can be determined under dynamic conditions. For two simple circuits simulations are presented which show the dynamic performance of an ideal controllable compensator with a control scheme based on the FBD Method.
Parametric approach for power measurements under non‐sinusoidal conditions
Authors: Offelli C. , Petri D. , Zanin F. E. 
Published: July 2010

AbstractThe determination of the power components under non‐sinusoidal conditions has received great attention in the last years. Digital instrumentation, provided of signal processing capability, allows to accomplish this task by evaluating the voltage and current spectral characteristics, from which all the needed power components can be derived. The paper presents a parametric method, based on a proper model for the input signal, able to perform the evaluation of the spectral components on the basis of data collected during short observation interval. This characteristic enhances the tracking capability of the estimation method and is useful when time‐varying conditions must be detected.
Formulating requirements for a universally applicable power theory as control algorithm in power compensators
Authors: Depenbrock M. , Marshall D. A. , Van Wyk J. D. 
Published: July 2010

AbstractDifferent power theories are examined, with regard to their applicability in controlling dynamic filters for non‐active power. Frequency‐domain approaches and a range of time‐domain approaches are considered, the latter being inherently more suitable for real‐time control of dynamic filters. Finally, some detailed attention is devoted to a combination of the approaches by Fryze, Buchholz and Depenbrock. This FBD‐approach leads to a general time‐domain resolution of power components in a generalized m‐wire system that can be used effectively in deriving control algorithms for dynamic filters of non‐active power.
Power theory of electric circuits: common data base of power related phenomena and properties
Authors: Czarnecki L. S. 
Published: July 2010

AbstractThis paper can be considered as an incentive for a cognition and discussion upon the very fundamentals of the power theory of electric circuits: what is the power theory; why there is a quest for it; what has been achieved; what still should be done. Also it is suggested that various power and current equations developed for describing power properties of electric circuits, in particular, circuits with non‐sinusoidal waveform of voltages and currents, as well as various conclusions and interpretations of power phenomena should not be considered as various power theories. They form rather a single power theory comprehended as a common data base of power related phenomena in electric circuits.
Error analysis based on the interaction between simulating charges in the csm for the electric‐field calculation of hv apparatus
Authors: Th. El‐Mohandes M. , Okubo H. 
Published: July 2010

AbstractThe purpose of this paper is to investigate the simulation accuracy sensitivity of electric field at each part of high‐voltage electrode which is often composed of multi‐electrode arrangements, using the charge simulation method (CSM). For the proper way of simulation, it is needed to introduce a boundary region at which the interaction between simulating charges become strong or negligible. The calculation results of estimating the simulation accuracy of electric field show distinguishable independent region even if the electrode parts are very close to each other. It is found that changing the charge arrangements in one part of the high‐voltage electrode, there is no influence to the calculation accuracy of electric field beyond this part. To improve the simulation accuracy of electric‐field calculation, the charge arrangements should be focused only to the part of electrode of interest.
Steady‐state security evaluation of electrical power systems by means of artificial neural network
Authors: Chiodo E. , Menniti D. , Testa A. , Picardi C. 
Published: July 2010

AbstractAn artificial‐neural‐network (ANN) application for steady‐state security evaluation of electrical power systems is presented. Such application is based upon a combined use of a multilayer back‐propagation neural network and of an opportune electrical system model, previously proposed by some of the authors. In the paper, the definition of steady‐state security and the problems arising from its on‐line evaluation are briefly recalled. Then, the ANN utilized is described with particular reference to the solutions adopted by the authors. Afterwards, some remarks on the system model utilized are reported. Finally, numerical applications on the AEP‐14 bus system are presented and the results obtained with different ANN configurations are analyzed.
Analytical expressions for current share in lightning protection systems
Authors: Orlandi A. , Piparo G. B. Lo , Mazzetti C. 
Published: July 2010

AbstractIn the present paper a circuit model is proposed, and validated, to simulate a Lightning Protection System (LPS) in which the distances between the down‐conductors and between the successive horizontal interconnecting rings are varied within a wide range of values. By the systematic application of the circuit model, solved by numerical methods, approximated expressions of current share functions are deduced. By means of such functions it is possible to identify how the lightning current is subdivided among the different conductors of an LPS with varying both the geometric configuration of the system and the typology of the grounding system. The share functions are validated by a series of experimental tests carried out on a real system placed on a building for its protection.
Optimal voltage/frequency control for space‐vector pwm three‐phase inverters
Authors: Lucanu M. , Neacsu D. 
Published: July 2010

AbstractThis paper presents an implementation algorithm of optimal space‐vector PWM in the case of conventional voltage/frequency control. The proposed command organization would radically save the memory used to store the pulse‐width constants. The controller implementation could be therefore achieved by any low‐cost microprocessor or microcontroller. The proposed method was verified by simulation.
Power‐quality improvement by static voltage booster
Authors: Quaia S. , Tosato F. 
Published: July 2010

AbstractAmong all the various types of possible disturbances affecting power quality in an electric supply (L e. spikes, frequency shift, harmonics etc.), the voltage dips are one of the most concerning because they can affect the regular operation of several widely diffused sensitive loads categories. Experience proves that most dips are characterized by a residual voltage at the delivery bus, where full outages (or micro‐interruptions) are only a small share. A remarkable improvement in the power‐supply quality can then be obtained by means of a cheap and simple static voltage booster (SVB), without energy storage, just able to sustain the voltage at the load bus bar during sag transients. In the paper this particular subject is investigated, trying to develop, among the various possible solutions, the most suitable SVB device to meet the target. The SVB dynamic performance has been tested by computer simulation, including the sag detection, control and firing system. In order to estimate the booster practical effectiveness in reducing the voltage sag's consequences, improving so the apparent utility power quality, the standard immunity characteristics of sensitive loads, like computers, and the SVB‐compensated voltage transients are compared and discussed.
Fast contingency evaluation method for generator outage simulation and power‐system security assessment
Authors: EL‐Emary A. , Arini Mahdi M. El , Alaily A. A. El 
Published: July 2010

AbstractIn order to speed up on‐line security assessment, a fast and accurate technique for on‐line generator outage simulation is presented in this paper. A linearized active power‐flow model is built up. After the generator outage, the active power of lost generator is distributed among the remaining units according to the frequency‐response characteristics (FRC) of individual units and loads taking into account the speed control actions of the unit governors. A linearized model of the automatic voltage regulator (AVR) and excitation system are used to derive the proposed steady‐state relation between the bus‐angle correction, obtained from the solution of active model using the redistributed power mismatch, and the corresponding changes in the voltage magnitudes. The quadratic power‐performance index for every generator outage is computed and the results are subsequently sorted in decreasing order according to the severity of effects. The proposed method is verified by applying it to a test system to show the ability of the proposed method to find the accurate solution and decrease in the computation time and memory storage required.
Comparison of two optimization techniques for the design of a three‐phase induction motor using three different objective functions
Authors: Faiz J. , Sharifian M. B. B. 
Published: July 2010

AbstractTwo optimization techniques, the simplex and Hooke‐Jeeves methods, are employed for optimum design of a 3.75 kW three‐phase induction motor. Three different objective functions, efficiency, cost and cost‐efficiency are used for this study. The obtained results are mainly compared in respect with their objective functions, but other design details have been also pointed out. Effects of stator‐ and rotor slot numbers and shape and the size of step in the search routine upon the optimum design are examined and discussed.
Comparison between finite‐element and traditional procedures for the prediction of busbar behaviour
Authors: Bottauscio O. , Chiampi M. , Chiarabaglio D. , Tartaglia M. 
Published: July 2010

AbstractThis paper investigates the multiconductor busbar behaviour under AC conditions with the aim of comparing the predictions of traditional circuit models with a more accurate analysis based on the electromagnetic field computation. This analysis employs a two‐dimensional finite‐element technique including eddy‐current effects. In linear systems this approach leads to a circuit model described by an impedance matrix, while, in presence of saturable media, field and circuit equations are simultaneously solved by a voltage‐driven field formulation. The paper analyses the behaviour of two different busbar systems when a short‐circuit current flows through them; the results obtained by the proposed approach are compared with those deduced according to the methods suggested by the IEC Standards and by the symmetrical components.