Damper Windings Research Articles

Harmonics of the Salient-Pole Synchronous Machine and Their Effects Part III. Differential Leakage of the Damper Winding with Respect to the Main Wave. Current Distribution in the Damper Bars

Harmonics of the Salient-Pole Synchronous Machine and Their Effects Part III. Differential Leakage of the Damper Winding with Respect to the Main Wave. Current Distribution in the Damper Bars

Harmonics of the Salient-Pole Synchronous Machine and Their Effects. Part I. MMF Harmonics Produced by the Armature and Damper Winding [includes discussion

Harmonics of the Salient-Pole Synchronous Machine and Their Effects. Part I. MMF Harmonics Produced by the Armature and Damper Winding [includes discussion

An Analysis of the Salient Pole Type Synchronous Machine with the Damper Windings

An Analysis of the Salient Pole Type Synchronous Machine with the Damper Windings

The design of high-speed salient-pole a.c. generators for water-power plants

The paper is a critical survey of the design of salient-pole generators in the speed range 300–1 000 r.p.m. with normal peripheral speeds of 15 000 ft/min and over, and runaway speeds of about double that figure. A Table of representative large machines is included.A review of the considerations governing the type of rotor body and the design of the pole fixing is followed by a discussion of the relative merits of laminated and solid poles and their influence on output. The design and construction of field coils is next considered with special reference to recent advances. Damper windings, ventilation and flywheel effect are also considered.The principles underlying the methods of subdividing the stator core and frame are given, and stator windings are considered in detail with particular reference to insulation, transposition and jointing.Bearing developments are reviewed, and the problem of mounting removable thrust collars on vertical shafts is discussed.The influence of various determining factors on the size of machine is analysed, and curves are included to show possible limits of output of future machines in comparison with those of the present day.

Analysis of unexcited synchronous capacitor motors

A capacitor-reluctance motor is a miniature salient-pole synchronous machine with a squirrel-cage damper winding and unsymmetrical stator windings connected in unsymmetrical circuits. The basic theories applicable to such a piece of synchronous machinery, namely, the symmetrical components, the 2-reaction theory, and the cross-field theory, are well established in engineering literature, and the purpose of this article is to deduce from these theories a comprehensive representation of the capacitor-reluctance motor from which the motor characteristics — for example, the starting torque, synchronous pull-out torque, torque angle, efficiency, and so forth — can be calculated readily with useful accuracy.

An Analysis or Unexcited Synchronous Capacitor Motors

A capacitor-reluctance motor is a miniature salient-pole synchronous machine with a squirrel-cage damper winding and unsymmetrical stator windings connected in unsymmetrical circuits. The basic theories applicable to such a piece of synchronous machinery, namely, the symmetrical components, the 2-reaction theory, and the cross-field theory, are well established in engineering literature, and the purpose of this article is to deduce from these theories a comprehensive representation of the capacitor-reluctance motor from which the motor characteristics — for example, the starting torque, synchronous pull-out torque, torque angle, efficiency, and so forth — can be calculated readily with useful accuracy.

Spring and Damping Coefficients of Synchronous Machines and Their Application

This paper develops simple formulas for spring and damping constants of synchronous machines. These formulas include the effects of induced currents in the damper winding and field. An approximation to the effect of primary resistance in producing a negative damping torque is given. An equivalent circuit is given which can represent accurately the mechanical system of several engine-driven generators or compressors operating in parallel. It is concluded that the conventional representation of synchronizing power as full-load power over full-load angle is sufficiently accurate for most cases, but that it is well to have a more accurate method for special cases.

Transients in 2-Phase Synchronous Machines

The analytical study of 3-phase synchronous machines has been well covered by man authors, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,2,3,4</sup> Not so much attention has been devoted to the 2-phase machine because much of the development of the methods of analysis occurred after the trend away from 2-phase systems was well established. Although the present use of 2-phase generators represents a small percentage of total generation, it is believed that there is some justification for analytical study of 2-phase machine performance. Such a study has value for the 2-phase systems now in use, and it has value in an analytical sense by showing how the relations developed for 3-phase generators may be adapted to generators with a different number of phases. The discussion in this paper is confined to L-connected, or quarter-phase machines with salient poles and without damper windings. It is limited to short-circuit or transient conditions. The inductances are defined and the relations expressing the variations of the several inductances of the windings are developed. The general fluxlinkage equations for all windings are determined in terms of stator and rotor currents. With this basis the operation of the machine under all possible short-circuit conditions is considered with the object of determining the transient and steady-state currents. The possible short-circuit conditions for the L-connected quarter-phase machine are the double line-to-neutral fault, the line-to-line fault, and the single line-to-neutral fault. The equations developed are compared with similar relations for 3-phase machines to show the similarities and the differences.

Discussion on “Tooth-ripple losses in unwound pole-shoes” and “Parasitic losses in synchronous-machine damper windings” before the Rugby Sub-Centre, 28th October, 1947

Discussion on “Tooth-ripple losses in unwound pole-shoes” and “Parasitic losses in synchronous-machine damper windings” before the Rugby Sub-Centre, 28th October, 1947

The authors' replies to the discussion on “Tooth-ripple losses in unwound pole-shoes” and “Parasitic losses in synchronous-machine damper windings”

The authors' replies to the discussion on “Tooth-ripple losses in unwound pole-shoes” and “Parasitic losses in synchronous-machine damper windings”

Corrigendum: Parasitic losses in synchronous-machine damper windings

Corrigendum: Parasitic losses in synchronous-machine damper windings

Parasitic losses in synchronous-machine damper windings

Parasitic losses in synchronous-machine damper windings

Parasitic losses in synchronous-machine damper windings

The paper develops, from theoretical considerations, formulae for the parasitic losses in both squirrel-cage and insulated phase-wound damper windings of synchronous machines. It shows that in squirrelcage windings the parasitic losses can be substantially reduced but not (except in one instance) eliminated, by a suitable choice of stator and rotor slot pitches; and that the losses in phase-wound dampers can, with little difficulty, be eliminated.Methods are given for calculating both the pulsation and the surface losses in the rotor-pole laminations, thus showing to what extent these losses are dependent on disposable machine constants. Numerical examples are worked out for two machines, and the results, together with those of two other machines, are given in the form of open-circuit core-loss curves on which test results are plotted for the purpose of comparison.

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.

Power Supply for Single-Phase Resistance Welders

THE rapidly increasing use of a-c contact welders in metal fabricating plants imposes single-phase low-power-factor fluctuating loads on plant power systems. The loads may range from a few kilo volt-amperes for a few cycles per weld, as in the case of a small spot welder, up to several thousand kilovolt-amperes for five to ten seconds per weld in the case of a large butt welder. Where the plant is supplied from a small private generating station, single-phase welding loads not only cause troublesome voltage fluctuations but may damage the damper windings of the generators. If power is purchased from a utility, voltage fluctuations may still be present, not only in the plant but often in the entire adjacent area. To eliminate such disturbances it has been necessary in numerous instances to install motor generators to serve as phase converters to supply single-phase power. It is the purpose of this paper to discuss the more common applications for single-phase welding generators and the electrical problems involved in each type of application.

Power supply for single-phase resistance welders

THE rapidly increasing use of a-c contact welders in metal fabricating plants imposes single-phase low-power-factor fluctuating loads on plant power systems. The loads may range from a few kilo volt-amperes for a few cycles per weld, as in the case of a small spot welder, up to several thousand kilovolt-amperes for five to ten seconds per weld in the case of a large butt welder. Where the plant is supplied from a small private generating station, single-phase welding loads not only cause troublesome voltage fluctuations but may damage the damper windings of the generators. If power is purchased from a utility, voltage fluctuations may still be present, not only in the plant but often in the entire adjacent area. To eliminate such disturbances it has been necessary in numerous instances to install motor generators to serve as phase converters to supply single-phase power. It is the purpose of this paper to discuss the more common applications for single-phase welding generators and the electrical problems involved in each type of application.

Generator Damper Windings at Wilson Dam

The majority of water-wheel generators now in service have been built without damper windings. Recent technical investigations and laboratory tests have indicated that, in addition to reducing oscillations and improving system stability, damper windings are very effective for reducing high-peak voltages during unbalanced short circuits. This applies particularly under switching conditions of clearing a fault when the load is disconnected from the distant end of a transmission line, and the charging current results in capacitive loading of the unfaulted phases. The existence of similar overvoltage conditions was recognized by the Wilson Dam operating staff and later confirmed by oscillograms during tests. This paper summarizes the studies and tests based on the observed overvoltage conditions and describes a method for adding damper windings to large water-wheel generators which are already installed. Short-circuit tests are extended to generators on a large scale which confirm the earlier theoretical and laboratory tests and demonstrate the advantages to be gained by adding damper windings to other water-wheel generators now in service. The tests show that damper windings in one generator when operated in parallel with another generator without dampers are effective in reducing high-peak voltages during unbalanced faults. Data are given to show the changes in machine reactances due to adding damper windings.

Generator Damper windings at Wilson Dam

Generator Damper windings at Wilson Dam

Unsymmetrical short circuits on water-wheel generators under capacitive loading

WATER-WHEEL GENERATORS without damper windings under capacitive load may have abnormally high voltages developed across their terminals at limes of unsymmetrical short circuits. These voltages are due to 2 causes. First, the difference in permeance of the magnetic circuit in the direct and quadrature axes produces, under unsymmetrical short circuits, distorted voltages which have high peak values even if there is no capacitance connected to the machine. Second, the capacitance of the line and the reactance of the machine resonate or partially resonate and produce still greater distortion of the voltages on the sound phase. The phenomenon associated with single-phase short circuits with no connected capacitive load, has been analyzed by Doherty and Nickle. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> The present paper is concerned with the effect of the capacitive load and an analysis of the factors involved in this phenomenon. Consideration is given to the system conditions under which these harmful voltages may arise and the remedial measures which may be applied for their elimination.