Dynamo-electric Machines Research Articles

Energy efficiency of coils heating of traction dynamoelectric machines during acceptance testing

The research concerns railway transport and devoted to the analysis of heating processes during the testing of the heating of dynamoelectric machines of rolling stock. The aim of the research is the decrease of power consumption for the after-repair acceptable tests of dynamoelectric machines by optimization of loading conditions. The estimation method of power efficiency of heating tests with the help of the index is suggested in the work. It represents the power relation, expended for the temperature increase of armature coil of electric machine, and the relation to the full loss in armature during the testing. The result of the differential equation of armature coil heating was the analytical formula for determination of the coefficient of the heating power efficiency according to the thermal parameters of the tested electric machine. To decrease the total power expenditure it was suggested to hold the test at load current higher than the watch value. It was shown that the increase of load current of tested electric machines to starting value helps to decrease total costs in their armatures almost one and a half time in comparison with the watch mode.

Method and apparatus to reduce operating noise of dynamo electric machines, particularly vehicular three-phase alternators

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Early electricity supply in Britain: Chesterfield and Godalming

The development of the ‘electric candle’ by Paul Jablochoff in 1876, and the improved dynamo-electric machines of Gramme, Siemens and others, led to the earliest street-lighting schemes in Paris in 1877 and further stimulated public interest in electric lighting at the Paris Electrical Exhibition one year later. From 1877 to 1881, over 100 experimental installations were set up in Britain, although very few achieved any permanence. The paper attempts to identify those schemes for public lighting which operated for more than 12 months, and examines the claims for priority of the towns of Chesterfield and Godalming which have frequently been cited as the first towns to be lit solely and completely by electricity.

Self-starting permanent-magnet a.c. motors

Many of the earliest dynamo-electric machines had permanent-magnet excitation. Gradually, however, this form of excitation was replaced by excitation from electromagnets, which seemed to offer the advantage of stronger magnetic fields and so more power from a total volume of material. Since then, many signs have appeared that indicate a reversal of this trend. Small permanent-magnet direct-current motors are commonplace in automobiles. Perhaps most interestingly, new forms of alternating-current machine using permanent magnets have begun to appear, and these show some interesting advantages compared with alternative drive systems. The self-starting permanent-magnet synchronous motor is essentially a new form of motor with a wide variety of applications

Electrical insulation particularly for use in winding slots of dynamo-electric machines and method for its manufacture: Fuchs, H. (Micafil A.G.) US Pat 3 974 314 (10 August 1976)

Electrical insulation particularly for use in winding slots of dynamo-electric machines and method for its manufacture: Fuchs, H. (Micafil A.G.) US Pat 3 974 314 (10 August 1976)

Dynamo-electric amplifiers with matric computor feedback control

The interconnection of dynamo-electric machines and analytic computers yields interesting and useful properties not available from either of the devices singly. Moreover, the homogeneity between Kron's modern matric-mathematical description of dynamo-electric machines on the one hand, and the mathematics pertinent to Matric Computors on the other hand, yields unity of concepts and notation. This is additionally exhibited by the ease with which dynamos and Matric Computors can rationally be combined into single electric networks. The objective of this didactic paper is to introduce the elemental concepts of the supermatric equation of state describing the interconnections of dynamo-electric amplifiers with Matric Computors, the latter being the control elements whose mathematical entries dominate the performance of the composite interconnected system.

Certain approaches to electromagnetic field problems pertaining to dynamo-electric machines

Current-carrying circuits in electrical rotating machines give rise to electromagnetic fields which are modified by surface polarities induced in adjacent ferromagnetic media and by eddy currents induced in neighbouring conducting media. The paper reviews certain approaches towards solving some of the electromagnetic problems involved and introduces a method for taking account of the reaction of eddy currents induced in a ferromagnetic medium on their inducing field.

Electrical essays: Motionally induced electric Fields — Part V: Relative motion of magnetic field and body

Jack, the physicist, is continuing his lectures to Alter Ego and his friends on the basic principles underlying dynamo-electric machines.

Discussion on “Calculation of the magnetic field in dynamo-electric machines by Southwell's relaxation method”

Discussion on “Calculation of the magnetic field in dynamo-electric machines by Southwell's relaxation method”

Calculation of the magnetic field in dynamo-electric machines by Southwell's relaxation method

Calculation of the magnetic field in dynamo-electric machines by Southwell's relaxation method

Calculation of the magnetic field in dynamic-electric machines by Southwell's relaxation method

A method of computing magnetic and electric fields is explained with reference to the problem of the magnetic flux distribution between stator and rotor of dynamo-electric machines. Mathematically, the problem is that of solving Laplace's or Poisson's equation. It is shown how approximate solutions are obtained with the help of a simple arithmetical technique. The differential equations are first replaced by a system of algebraic equations which are then solved by means of a computation method due to R. V. Southwell. The computation process is outlined and illustrated by a simple example which shows all the essential steps involved. A solution is given for two idealized examples of pole shoe and armature for which rigorous solutions are known. The agreement between the rigorous and approximate solutions is found satisfactory. Sharp corners of pole shoe and armature present a problem for which various solutions are possible; some of these are indicated. The flux distribution of a complete machine is computed and presented as an example of a complex problem not amenable to a rigorous solution.

Field-pole leakage flux in salient-pole dynamo-electric machines

In this paper the authors investigate the problem in salient-pole dynamo-electric machines of flux passing from field pole-tip to pole-tip without linking the armature winding. This flux, designated “pole-tip leakage,” is of broad interest in determining both transient and steady-state performance characteristics of salient-pole dynamo-electric machines.The problem is treated as one of two' dimensions and the method of conformal transformation is used to obtain results in the form of elliptic functions. Numerical results are obtained by a method of cross-plotting and given in curve form for the usual range of variables. The curves have been used in the design of machines for 5 years, and the great number of test-results obtained have been found to be in very satisfactory agreement with the calculations.

Predetermination of self-cooled oil-immersed: Transformer temperatures before conditions are constant

The temperature rises of dynamo electric machines, in changing from one steady thermal state to another, follow an exponential law of the form 1 − ∊ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−βt</sup> , where 1/β is the thermal time constant, or the time required to attain 63. 2 per cent of the final change in temperature rise. It is shown here that while the winding temperature rise over room of self-cooled oil-immersed transformers follows this law only after a certain time has elapsed, quite accurate results may be obtained by calculating the time-temperature curves of the top oil temperature rise above room, and the winding temperature rise above top oil separately, since each follows the above exponential law quite closely, then adding them together to get the winding temperature rise above room at any time before conditions are constant. A procedure is explained in detail for calculating β, for either the lop oil rise or the winding rise above top oil from the weights of materials the iron and copper losses and the winding and top oil constant temperature rises at any given load. Comparisons of temperatures by test and calculation are presented.

Predetermination of Self-Cooled Oil-Immersed Transformer Temperatures Before Conditions are Constant

The temperature rises of dynamo-electric machines, in changing from one steady thermal state to another, follow an exponential law of the form 1 - ϵ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-ßt</sup> , where 1/ß is the thermal time constant, or the time required to attain 63. 2 per cent of the final change in temperature rise. It is shown here that while the winding temperature rise over room of self-cooled oil-immersed transformers follows this law only after a certain time has elapsed, quite accurate results may be obtained by calculating the time-temperature curves of the top oil temperature rise above room, and the winding temperature rise above top oil separately, since each follows the above exponential law quite closely, then adding them together to get the winding temperature rise above room at any time before conditions are constant. A procedure is explained in detail for calculating ß, for either the top oil rise or the winding rise above top oil from the weights of materials the iron and copper losses and the winding and top oil constant temperature rises at any given load. Comparisons of temperatures by test and calculation are presented.

Dr. Henry Wilde, F.R.S.

DR. HENRY WILDE, whose death was announced in NATURE of April 3, was a man of remarkable individuality and a pioneer in electrical engineering. He was born in Manchester in 1833. During his apprenticeship he experimented with voltaic cells, electrical machines, electrical kites, and the electro-deposition of metals. He soon realised the great commercial possibilities of the applications, of electricity, and he decided, when, he was twenty-three years of age, to commence in business as a telegraph engineer and lightning-conductor expert. Several years o were devoted to the invention of a magneto-electrie alphabetic telegraph. Experiments with electro-magnets led to the design of an improved electrid generator described in his patents of 1863 and 1865. Wilde's “dynamo-electric machines”—as they were named by Charles Brooke, F.R.S.—quickly replaced batteries for electro-deposition ooo.lid arc lighting, but in use they had the serious disadvantage of becoming very hot. In the endravour to cure this fault Wilde designed a very different type of dynamo. This was a multipolar machine, with sixteen pairs of electro-magnets, which was made self-exciting by a “minor” current from four of the armature bobbins. Both this and the earlier machine were used by Elkington for the electrolytic refining of copper.

Critical review of the bibliography on unbalanced magnetic pull in dynamo-electric machines

Critical review of the bibliography on unbalanced magnetic pull in dynamo-electric machines

Critical Review of the Bibliography on Unbalanced Magnetic Pull in Dynamo-Electric Machines

The purpose of this paper is to serve as an introduction to the succeeding comprehensive article by Mr. E. Rosenberg, on the subject of Magnetic Pull in Electric Machines. The Maxwell equation, upon which all of the formulas for unbalanced magnetic pull are based, is first established. A critical review is then given of the articles pertaining to this subject, which have appeared in the technical press to date. It is pointed out wherein the various expressions which have been proposed differ from one another and to what extent they are consistent.

The predetermination of the performance of dynamo-electric machinery

This paper opens a discussion on general methods of calculating dynamo-electric machines and gives an outline of a method which is applicable to all types of such machines, whether alternating-current or continuous-current generators or motors, or rotary converters. Simple rules are given for determining the various quantities upon which the performance of a machine depends; in particular, the method of arriving at a temperature rise which may be expected is more completely developed than in a previous paper by H.D. Symons and the author.

Characteristics and applications of vibration galvanometers

In the vibration galvanometer we have a type of synchronous motor which is distinctly different from all the ordinary types of dynamo electric machines. Further it does not have any of the characteristics of any of the ordinary galvanometers and except for the fact that it is used in the detection or measurement of small currents and voltages, it should not be called a galvanometer. In galvanometers, except when used in the measurement of transient currents or quantity of electricity, the moving system is displaced until we have an equality of static couples acting on it. In the vibration galvanometer the equilibrium condition is an equality between integral values of the product of the current and generated voltage and the mechanical power dissipated in various ways as in ordinary electric motors when operated without a load. It therefore behaves more like an electric motor than like a galvanometer. Further, since it is used only with alternating currents and operates in synchronism with the current it must necessarily have some of the characteristics of a synchronous motor. As a motor the efficiency of conversion was found in a particular case to be as high as 97½ per cent while the power required to maintain an easily discernable amplitude of vibration was of the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−11</sup> watts. One of the large turbo-generators would therefore furnish the power necessary to operate a thousand-million-billion such machines.

Characteristics and Applications of Vibration Galvanometers

In the vibration galvanometer we have a type of synchronous motor which is distinctly different from all the ordinary types of dynamo electric machines. Further it does not have any of the characteristics of any of the ordinary galvanometers and except for the fact that it is used in the detection or measurement of small currents and voltages, it should not be called a galvanometer. In galvanometers, except when used in the measurement of transient currents or quantity of electricity, the moving system is displaced until we have an equality of static couples acting on it. In the vibration galvanometer the equilibrium condition is an equality between integral values of the product of the current and generated voltage and the mechanical power dissipated in various ways as in ordinary electric motors when operated without a load. It therefore behaves more like an electric motor than like a galvanometer. Further, since it is used only with alternating currents and operates in synchronism with the current it must necessarily have some of the characteristics of a synchronous motor. As a motor the efficiency of conversion was found in a particular case to be as high as 97½ per cent while the power required to maintain an easily discernable amplitude of vibration was of the order of 10 −11 watts. One of the large turbo-generators would therefore furnish the power necessary to operate a thousand-million-billion such machines.