Performance Of Synchronous Machine Research Articles

New approach to the determination of synchronous-machine parameters from tests

In the last decade or more, a number of tests on large synchronous machines and the associated analytical work have revealed certain inaccuracies in the theory of synchronous-machine performance, which has been used for the last half century. A new look is taken at the assumptions underlying the old theory and several of them are discarded in the derivation of a new theory which corrects many of the inaccuracies. The new theory results in new formulas for the calculation of machine parameters, such as transient reactance and transient time constant; it is particularly relevant in the calculation of parameters for synchronous machines with damper windings.

Analysis of asymmetrical faults in synchronous generators by d-q-0 frame of reference

The paper describes the development of a mathematical model in the d-q-0 frame of reference for the analysis of unbalanced operation of synchronous machines. The equations for faults between two phases and between one line and the generator neutral are described. The solution of the equations of the model by digital computer is presented. Initially, the model neglects nonlinearities and subtransients in the synchronous generator. The validity of the method of analysis developed is examined by comparing the computed results with the test results for a 7 MW generator and a 50 MW generator.

Theoretical and Experimental Analysis of Operating Point Stability of Synchronous Machines

A stability study of synchronous machine operation is made by applying Routh's criterion to the linearized equations describing behavior for small perturbations about a steady state operating point. Two special cases for non salient-pole machines are examined and experimental confirmation of the predicted stability boundaries is given. Salient pole machines with both d and q-axis damper windings are also investigated. Results illustrating the effect of frequency, load torque, rotor inertia, stator resistance, and other machine parameters and constraints are included and suggestions regarding improved performance are given.

Some aspects of generator backup protection in relation to synchronous-machine performance during h.v.-system faults

The fault performance of large generator units is considered in relation to the selection of generator-backup-protection settings, and a method of determining protection performance is presented, based on a simplified analysis of generator fault currents and neglecting rotor-angle swings. The validity of this approach is demonstrated and the method is used to determine the fault performance of negative-phase-sequence current and overcurrent protection. Alternative methods of overcurrent protection are examined which appear to provide improved backup protection for internal and external faults.

Synchronizing Power of a Synchronous Machine Operating on Infinite Bus-Bars

Synchronizing Power of a Synchronous Machine Operating on Infinite Bus-Bars

Contribution to the Theory of Asynchronous Performance of Synchronous Machines with Salient Poles: Part II Analysis of MMF and Magnetic Field Angular Velocity. Power and Torque Equations

The present work is a continuation of a study presented by one of the authors at the 1969 IEEE Winter Power Meeting in New York, N. Y. In that part of the paper the MMF and air gap magnetic field space variations, and the phase current time variations of a salient pole synchronous machine in asynchronous operation were analyzed. Here, the MMF and magnetic field angular velocity, as well as the power and torque as a function of slip, are considered.

Dynamic performance of synchronous machines in control systems

Synchronous motors appear to offer a number of advantages over induction motors when used on variable-frequency supplies for the final drive of a high-power servo. The paper examines two aspects of such drives relevant to synchronous motors when so used; limiting acceleration and frequency-response characteristics, and their dependence on certain pertinent variables such as field excitation and amplitude of excursion. Analytical and semianalytical methods, backed by experimental results, are given to predict the dynamic behaviour of synchronous motors.

Contribution to the Theory of Asynchronous Performance of Synchronous Machines with Salient Poles: Part I - Analysis of MMF and Magnetic Field Space Variations, and Armature Current Time Pulsations

Asynchronous transients of a salient pole synchronous machine are studied in this paper. The results of the theoretical analysis, justified by both analog computer and experimental means, are used in explaining the airgap magnetic field space variations and the phase current time variations that occur in a synchronous machine with salient poles during its asynchronous starting transient. This study can also be applied in analyzing other phenomena of synchronous machine transients, for instance, speed-torque characteristics, and magnetic field angular velocity as a function of slip.

Stability Analysis for Variable Frequency Operation of Synchronous Machines

A stability study of a synchronous machine is performed by applying the Nyquist stability-criterion to the equations which describe the behavior of the machine during small displacements about a steady-state operating point. This investigation reveals that, in some cases, machine instability can occur at low operating speeds. Regions of machine stability are established from the results of a digital computer study and the maximum resonance peak Mm is used as a criterion for determining relative stability when the response of the electromechanical system is damped. The effect on machine stability for changes in different system parameters is given. Also, the maximum resonance peak is used to establish an equivalent second-order electromechanical system. The response of this system is found to compare favorably to that of an idealized synchronous machine at any operating speed.

Asynchronous Operation of an Iteratively Structured General-Purpose Digital Computer

The preceding paper proposed a general-purpose digital computer structure consisting of many small iteratively connected sequential machines. A set of machine instructions was presented and a programming example of synchronous machine operation was given. This paper examines some of the problems associated with asynchronous operation of this iteratively structured digital computer. A solution is presented enabling the many small sequential machines which constitute the large iterative computer to communicate asynchronously. The instruction set outlined in the previous paper is maintained and a pictorial example of asynchronous operation is presented.

General Application of the Constant Flux Linkage Theorem to the Transient Performance of Synchronous Machines

General Application of the Constant Flux Linkage Theorem to the Transient Performance of Synchronous Machines

Simulation of salient-pole synchronous machines on the network analyser

A new electronic device for the simulation of performance of synchronous machines with salient poles on the network analyser is described, which, the authors believe, has advantages, as far as construction and accuracy are concerned, over similar ones described up to now. The accuracy of the simulator is shown in numerical examples and formu'as are given for calculating errors for other cases.

Asynchronous and single-phase operation of synchronous machines

ASYNCHRONOUS operation of synchronous machines has been the subject of numerous articles in the technical literature, for example, the articles of Fechheimer, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> Hay and Mowdawalla, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Putman, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Park, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> Linville, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> Lauder <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> . The fact that articles on this subject continue to be of primary interest to design and operating engineers is attributable to the importance of satisfactory operation at asynchronous speeds. It is only through a precise knowledge of the conditions present in asynchronous operation that machines can be designed for and operated through these asynchronous periods satisfactorily. As examples of the extreme conditions which can arise during asynchronous operation, it should be noted that stalling a synchronous machine with the field voltage applied can result in pulsating torques greater than those obtained by inadvertent synchronizing 180° out of phase; <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> or that the currents in the damper bars on the trailing half of a pole can be considerably greater than the currents in the corresponding bars on the leading half of the pole, and the resulting unequal heating will influence the design of the damper winding to a considerable degree. Because of the importance of these and similar phenomena, the problem of asynchronous operation must be studied continuously until a complete, easily visualized, and easily applied solution is obtained.

Asynchronous and Single-Phase Operation or Synchronous Machines

ASYNCHRONOUS operation of synchronous machines has been the subject of numerous articles in the technical literature, for example, the articles of Fechheimer,1 Hay and Mowdawalla,2 Putman,3 Park,4 Linville,5 Lauder6. The fact that articles on this subject continue to be of primary interest to design and operating engineers is attributable to the importance of satisfactory operation at asynchronous speeds. It is only through a precise knowledge of the conditions present in asynchronous operation that machines can be designed for and operated through these asynchronous periods satisfactorily. As examples of the extreme conditions which can arise during asynchronous operation, it should be noted that stalling a synchronous machine with the field voltage applied can result in pulsating torques greater than those obtained by inadvertent synchronizing 180° out of phase;6 or that the currents in the damper bars on the trailing half of a pole can be considerably greater than the currents in the corresponding bars on the leading half of the pole, and the resulting unequal heating will influence the design of the damper winding to a considerable degree. Because of the importance of these and similar phenomena, the problem of asynchronous operation must be studied continuously until a complete, easily visualized, and easily applied solution is obtained.

Inherent errors in the determination of synchronous-machine reactances by test

AS PROGRESS in the design and in the calculation of performance of synchronous machines has been made it has become necessary to specify their characteristics with continually greater accuracy. The predetermination of short-circuit currents, voltage dip on sudden application of load, stability characteristics during system disturbances, excitation requirements, and many other characteristics has been made possible by the development of an adequate theory, confirmed and refined by operating and test experience. The machine characteristics commonly used to predict performance usually are specified in terms of various reactances and time constants. As the number of these quantities and the accuracy to which they must be known has increased, certain inconsistencies among methods of definition, calculation, and test have become apparent. These should ideally all result in the same value. If they differ, one naturally would be inclined to consider the test value as the true reactance. In any case in which a reactance of a particular machine is specified, a method of testing for that reactance also must be specified, and any other definition of the reactance has little practical significance. In this sense the criterion of a good method of calculating the reactance is that it predict as nearly as possible the value which will be found by the specified test method. It, of course, can be asked legitimately whether the specified reactance is the proper one in view of the use to which it is to be put, and the definition is intended to describe the reactance so as to answer this question.

Inherent Errors in the Determination of Synchronous-Machine Reactances by Test

AS PROGRESS in the design and in the calculation of performance of synchronous machines has been made it has become necessary to specify their characteristics with continually greater accuracy. The predetermination of short-circuit currents, voltage dip on sudden application of load, stability characteristics during system disturbances, excitation requirements, and many other characteristics has been made possible by the development of an adequate theory, confirmed and refined by operating and test experience. The machine characteristics commonly used to predict performance usually are specified in terms of various reactances and time constants. As the number of these quantities and the accuracy to which they must be known has increased, certain inconsistencies among methods of definition, calculation, and test have become apparent. These should ideally all result in the same value. If they differ, one naturally would be inclined to consider the test value as the true reactance. In any case in which a reactance of a particular machine is specified, a method of testing for that reactance also must be specified, and any other definition of the reactance has little practical significance. In this sense the criterion of a good method of calculating the reactance is that it predict as nearly as possible the value which will be found by the specified test method. It, of course, can be asked legitimately whether the specified reactance is the proper one in view of the use to which it is to be put, and the definition is intended to describe the reactance so as to answer this question.

Transactions section: Preprint of corresponding pages from the current annual AIEE transactions volume: Saturated synchronous machines under transient conditions in the pole axis

THE performance of synchronous machines in steady-state operation, as well as in the transient state, is substantially determined by magnetic saturation in their iron circuits.13,14,20 It is well-known that high initial and sustained short-circuit currents develop under widely different conditions of saturation and that large capacitive loading is unstable but for the effect of saturation.

A Stroboscopic Power Angle Recorder

An automatic stroboscopic power angle recorder developed to study directly the transient performance of synchronous machines during load disturbances is described in this paper. A portion of the machine under observation is illuminated by stroboscopic light, and its oscillations are recorded directly by a moving-film camera. The operation of the device is made automatic by connecting a suitable relay in its circuit. A typical installation on a hydroelectric generator is described.

A stroboscopic power angle recorder

An automatic stroboscopic power angle recorder developed to study directly the transient performance of synchronous machines during load disturbances is described in this paper. A portion of the machine under observation is illuminated by stroboscopic light, and its oscillations are recorded directly by a moving-film camera. The operation of the device is made automatic by connecting a suitable relay in its circuit. A typical installation on a hydroelectric generator is described.

Determination of Synchronous Machine Constants by Test Reactances, Resistances, and Time Constants

In recent years there have been many advancements made in the art of analysis of three-phase synchronous machine operation. Most treatments to date have very properly stressed the theoretical point of view, the practical point of view receiving less attention due in part to the complications involved, particularly those due to saturation effects. In this paper the practical stand-point is stressed and discussed on the basis of observations made from many tests; an important feature of these tests is that saturation effects under short circuit were studied by applying short circuits to machines operating at rated voltage. Due to serious saturation effects, the so-called constants of synchronous machines may have different values under different conditions. What are considered to be the most important of these values are discussed, and by defining certain saturated and other values, an attempt is made to provide a definite basis for the specification of machine constants. Part I reviews certain basic concepts and discusses practical considerations of test methods. Part II describes methods of determining the more important constants by test. Part III illustrates the application of these methods to actual power machinery, and presents tabulated test results as well as a table of typical constants. The Appendixes are devoted to certain additional tests and conclusions, and to development of formulas.