DOI:10.1049/pi-a.1962.0065

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-a.1962.0067

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-a.1962.0068

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Generalized rotating-field concepts, developed in an earlier paper, are used to analyse the behaviour of a single-phase induction motor having asymmetrical stator windings not in quadrature. The analysis includes the effects of the air-gap harmonic fields and is applicable for all values of the turns ratio,k, and the displacement angle, θ. It is shown that the generalized equations of performance reduce to those obtainable by other methods for the few special combinations ofkand θ where the latter could be accurately applied. The starting performance of the motor is expressed in terms of dimensionless parameters, and the effect of θ on the starting torque is discussed in some detail. It is shown that though more starting torque is obtained by making θ greater than 90°, the magnitude of the increase depends upon the rotor resistance and the effects of the harmonic fields. Tests on standard machines show good agreement with theoretically predicted performance.

DOI:10.1049/pi-a.1962.0069

出版商:IEE    

年代:1962

数据来源: IET

摘要:

It is shown that the performance of an induction motor, having a symmetrically wound rotor and a stator which may be wound or connected in any conceivable way, can be uniquely specified by means of two sets of equations. The first set, the ‘internal’ equations, is peculiar to the machine and expresses the phase voltages in terms of the phase currents and rotating-field parameters. These are based on a generalization of the counter-rotating field theory to include the effects of all space harmonics. The second set—the ‘external’ equations—is peculiar to the connection and expresses the relationships between the phase voltages and currents, supply voltages and line impedances. These are the so-called ‘inspection equations’ obtained by the simple application of Kirchhoff's laws. The complete performance of the machine can always be computed from the solutions of the two sets of equations on a phase-by-phase basis. It is also shown that, if the stator has windings whose axes are symmertically displaced, symmetrical-component theory is an alternative which enables to be computed on a per-phase basis whilst still including the effects of all space harmonics.

DOI:10.1049/pi-a.1962.0070

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The deterioration of the insulation in high-voltage turbo-generator stators can be followed by means of non-destructive tests. The relative merits of the available methods of testing stator insulation are given, but at present a single test will not reliably indicate the insulation condition. The detection of discharges with an electronic instrument most closely approaches this ideal and has the unique ability of indicating the existence of preferential deterioration near the line terminals of a high voltage stator. A dependable guide to the insulation condition can be obtained only from considering the results of several tests, employing both alternating and direct current. This allows the variation in the insulation of a turbo-generator stator undergoing normal usage to be determined. Departure from the normal variation indicates those machines that have suffered abnormal deterioration.The presence of deleterious discharges in high-voltage bushings at the time of manufacture has been ascertained with the E.R.A. discharge detector. The discharge magnitude is measured directly and has been related to the indirect methods normally used, such as loss angle and audible hiss. For synthetic-resin-bonded-paper bushings of 33–132kV rating, some discharges are permissible near the working voltage. Discharges in oil-impregnated-paper bushings of 132, 220 and 330kV rating, however, are undesirable at the maximum working voltage. Recommendations are made of the permissible discharge magnitude for the two types of bushings.

DOI:10.1049/pi-a.1962.0073

出版商:IEE    

年代:1962

数据来源: IET

摘要:

For a short period following are interruption, reignition can be produced by a continuous energy process. The paper develops the theory of measurements of are resistance, power loss and reignition voltage during this thermal reignition period of recovery. Experiments are described in which these measurements are made during the first 100μs of the free recovery of ares in air burning freely between 4mm diameter carbon electrodes. Direct-current pulses of 150 ms duration and of 10, 20 and 40A are used.The results give variations in resistance, power loss and reignition voltage which in the main can be explained by thermal considerations, although the first few microseconds of recovery are difficult to explain in a like manner. A clear distinction is drawn between power-loss voltage and reignition voltage.Assuming a linear relationship between the internal energy and the electrical conductivity of a thermal gas, a linearized theory of interruption is developed which appears to have advantages over previous interruption theories and shows reasonable agreement with the experimental results.

DOI:10.1049/pi-a.1962.0074

出版商:IEE    

年代:1962

数据来源: IET

摘要:

An apparatus is described with which magnetostrictive changes of length in strip samples can be measured with accuracy under direct and alternating conditions at various flux densities.The factors controlling the magnetostrictive pattern in grain-oriented silicon-iron have been studied. It has been found that considerable reduction in magnetostriction can be obtained by heat treatment at a suitable temperature, the time at temperature and the rate of cooling both having an effect on the ultimate value of the magnetostriction. With material heat-treated under optimum conditions, cooling under an applied load and magnetic annealing give no subsequent reduction.Tensile stress applied along the direction of flux produces a marked decrease in magnetostriction, as does, to a smaller extent, compressive stress applied at right angles to the sheet. It is found that a compressive stress of only 3001bf/in2along the direction of flux is very deleterious, so that in transformer construction the use of wavy or undulating sheets, which on clamping would have such induced stress components, should be avoided. Bending and handling have little effect on the material, provided that it is restored to its original form and that the applied stresses have caused no permanent deformation.The importance of these measurements to the transformer engineer is discussed.

DOI:10.1049/pi-a.1962.0076

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The case for routine analysis of engineering problems by digital computers is now firmly proven. Programming in terms of the special semi-mathematical codes now available for large computers is particularly suited to the needs of engineers who are not professional programmers. In fact, for development work such as that described in the paper, the engineer with his knowledge of the physical significance of the mathematical expressions involved, has a considerable advantage.The authors describe their experience in the digital solution of two of the main problems encountered in power-system analysis, namely load-flow and short-circuit investigations. Use has been made of matrix algebra in combination with iterative methods, and the techniques evolved, which have been proved commercially feasible, are set out, with an indication of possible future developments.

DOI:10.1049/pi-a.1962.0078

出版商:IEE    

年代:1962

数据来源: IET