DOI:10.1049/ji-2.1947.0001

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The various losses produced by flux oscillations in the unwound pole-face are considered for three main types of shoe, namely the solid ungrooved, the solid grooved and the laminated. The treatment is theoretical and includes in particular an examination of the evaluation of the amplitude of flux oscillation, the quantitative effect of harmonics, and the method of dealing with the permeability, which is a variable quantity.The losses considered are those due to eddy currents, to hysteresis and to pulsations; it is found that in normal designs only eddy-current loss has importance. The resulting equations are applied to independently published experimental results, and the calculation of a typical alternator is included showing the effect of grooving both by theory and by test. These applications confirm the general validity of the equations.

DOI:10.1049/ji-2.1947.0002

出版商:IEE    

年代:1947

数据来源: IET

摘要:

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.

DOI:10.1049/ji-2.1947.0003

出版商:IEE    

年代:1947

数据来源: IET

摘要:

A method of determining the d.c. magnetization characteristic of a laminated core using overlapping joints, when the mean flux density is less than half the saturation value, has been given by Phear and Mallock. This method is now extended to include any value of the mean flux density and to increase the accuracy of calculation over the range covered by Phear and Mallock, their work being followed to the fullest possible extent in the present paper.The results are expressed in terms of the increase per joint of the total m.m.f. of the core with varying mean flux density, since in this form they can be applied directly to determine the d.c. magnetization characteristic of any laminated core.Calculated and test results applicable to Mumetal only are given in the present paper, but bearing in mind the change in the ferric saturation value, the conclusions become generally applicable to other magnetic materials such as the silicon-iron steels.Among other important conclusions arrived at is the result that it is possible for a plain butt joint to require a smaller increase in m.m.f. than an overlap joint over quite an appreciable range of the mean flux density.

DOI:10.1049/ji-2.1947.0005

出版商:IEE    

年代:1947

数据来源: IET

摘要:

A description is given of a method of measuring the velocity of sea-water, using the fundamental law of electrodynamics, regarding the water as a conductor and measuring the e.m.f. generated when it moves relative to a magnetic field.Descriptions are given of an underwater unit for producing the magnetic field, apparatus for measuring the motive e.m.f. and experiments made with the unit in a flume in order to calibrate it. It is shown that the method is very convenient for comparing velocities and can be used for the measurement of water velocities due to swell, tidal current, etc.

DOI:10.1049/ji-2.1947.0027

出版商:IEE    

年代:1947

数据来源: IET