Pub Date : 1947-06-01DOI: 10.1049/JI-3-2.1947.0041
D. Tucker
A circuit is described which permits a highly-selective transmission-measuring equipment to be designed to meet a specified accuracy of measurement; it is suggested that ±0.25 db is quite readily obtainable. The basic principles of the method are (a) the direct demodulation of the test signal by means of an identical frequency obtained from an oscillator synchronized to the test tone, (b) discrimination against unwanted line signals obtained by means of low-pass filters, (c) the elimination of the effect of the phase difference between the test and demodulating tones by Barber's two-path method, and (d) the use of an envelope-modulated test signal.
{"title":"Highly-selective transmission-measuring equipment for communication circuits","authors":"D. Tucker","doi":"10.1049/JI-3-2.1947.0041","DOIUrl":"https://doi.org/10.1049/JI-3-2.1947.0041","url":null,"abstract":"A circuit is described which permits a highly-selective transmission-measuring equipment to be designed to meet a specified accuracy of measurement; it is suggested that ±0.25 db is quite readily obtainable. The basic principles of the method are (a) the direct demodulation of the test signal by means of an identical frequency obtained from an oscillator synchronized to the test tone, (b) discrimination against unwanted line signals obtained by means of low-pass filters, (c) the elimination of the effect of the phase difference between the test and demodulating tones by Barber's two-path method, and (d) the use of an envelope-modulated test signal.","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"284 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122968644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper develops a graphical method of determining the short-circuit current of an inductor alternator, taking into account the effect of a damping circuit which prevents oscillations of the total flux. It is shown that the short-circuit current depends mainly on the important ratio of maximum to minimum flux and on the leakage. The equivalent circuit for the inductor alternator is determined from the open-circuit voltage and short-circuit current. The ratio of these values varies owing to saturation effects, but can be taken as constant for a given excitation and independent of the load circuit. Compensation of the internal inductive reactance by series condensers for an alternator with constant and variable speed is considered, and the transient- and steady-voltage changes are investigated. The reason for the voltage drop of the fully compensated machine being many times greater than the resistive drop is given. The effect on the speed/torque characteristic of series-condenser compensation is shown. The paper explains that the damping winding increases the effective excitation for a load circuit having a lagging power factor and reduces for a leading power factor. An unusual type of instability arising when paralleling series-compensated alternators is investigated, and a remedy for this phenomenon is given.
{"title":"Short-circuit characteristics and load performance of inductor-type alternators","authors":"A. Mandl","doi":"10.1049/JI-2.1947.0047","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0047","url":null,"abstract":"The paper develops a graphical method of determining the short-circuit current of an inductor alternator, taking into account the effect of a damping circuit which prevents oscillations of the total flux. It is shown that the short-circuit current depends mainly on the important ratio of maximum to minimum flux and on the leakage. The equivalent circuit for the inductor alternator is determined from the open-circuit voltage and short-circuit current. The ratio of these values varies owing to saturation effects, but can be taken as constant for a given excitation and independent of the load circuit. Compensation of the internal inductive reactance by series condensers for an alternator with constant and variable speed is considered, and the transient- and steady-voltage changes are investigated. The reason for the voltage drop of the fully compensated machine being many times greater than the resistive drop is given. The effect on the speed/torque characteristic of series-condenser compensation is shown. The paper explains that the damping winding increases the effective excitation for a load circuit having a lagging power factor and reduces for a leading power factor. An unusual type of instability arising when paralleling series-compensated alternators is investigated, and a remedy for this phenomenon is given.","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115056429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A calibration is given for spark-gap electrodes designed to ensure that the spark path lies in a uniform field, and it is shown that for all three sizes of electrodes investigated, covering a range of 9 to 315 kV (peak), the sparkover voltages are within 0.2% of the values given by the empirical lawV=24.22S+6.082√SkV (peak) at 20°C and atmospheric pressure of 760 mm Hg, where S is the electrode spacing in centimetres.All observations were made with vertical gaps having the lower electrode connected to earth, and comparative data were obtained for a sphere gap with electrodes 25 cm in diameter. The effects of surrounding objects and of faulty alignment of the electrodes were determined experimentally, and on the basis of these results a number of recommendations are made, giving the limits within which the spark-over voltage is defined by the above equation.
对火花间隙电极进行了校准，以确保火花路径位于均匀场中，结果表明，对于所有三种尺寸的电极，覆盖9至315 kV(峰值)的范围，在20°C和760 mm Hg的大气压下，火花电压在经验定律v =24.22S+6.082√SkV(峰值)给出的值的0.2%以内，其中S为电极间距，单位为厘米。所有的观测都是在下电极与地面连接的垂直间隙中进行的，并获得了直径为25厘米电极的球形间隙的比较数据。通过实验确定了周围物体和电极错误对准的影响，并在这些结果的基础上提出了一些建议，给出了由上述方程定义的火花过电压的限制。
{"title":"Calibration of uniform-field spark-gaps for high-voltage measurement at power frequencies","authors":"F. M. Bruce","doi":"10.1049/JI-2.1947.0052","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0052","url":null,"abstract":"A calibration is given for spark-gap electrodes designed to ensure that the spark path lies in a uniform field, and it is shown that for all three sizes of electrodes investigated, covering a range of 9 to 315 kV (peak), the sparkover voltages are within 0.2% of the values given by the empirical lawV=24.22S+6.082√SkV (peak) at 20°C and atmospheric pressure of 760 mm Hg, where S is the electrode spacing in centimetres.All observations were made with vertical gaps having the lower electrode connected to earth, and comparative data were obtained for a sphere gap with electrodes 25 cm in diameter. The effects of surrounding objects and of faulty alignment of the electrodes were determined experimentally, and on the basis of these results a number of recommendations are made, giving the limits within which the spark-over voltage is defined by the above equation.","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123195903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The author's reply to the discussion on 'The design of an ellipsoid voltmeter for the precision measurement of high alternating voltages' and 'Calibration of uniform-field spark-gaps for high-voltage measurement at power frequencies'","authors":"F. M. Bruce","doi":"10.1049/JI-2.1947.0054","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0054","url":null,"abstract":"","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126419244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The authors' replies to the discussion on \"Recent progress in the design of the high-voltage overhead lines of the British grid system\" and \"Cable terminations\"","authors":"W. Nicholls, D. B. Irving","doi":"10.1049/JI-2.1947.0050","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0050","url":null,"abstract":"","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121898441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The design of machines for medium-frequency power circuits, increasingly used in industry and in aircraft, demands a knowledge of flux-penetration phenomena as affecting both the iron losses and the utilization of the available iron section. The paper shows how hysteresis influences all important quantities, especially the eddy-current loss, the apparent flux, and the utilization factor. Theoretical expressions for these are, on certain assumptions, rather simply derived and presented in a form convenient for use in laboratories and design offices. Curves are given for this purpose, and the ranges of frequency and thickness indicated over which the influence of hysteresis on the other quantities is pronounced. Systematic collection of test results showing their departure from the theoretical values would assist in elucidating the relation of the discrepancies to the grain structure and the metallurgical history of the sheet.
{"title":"Medium-frequency magnetization of sheet steel: the interdependence of hysteresis, eddy currents and magnetic utilization","authors":"R. Pohl","doi":"10.1049/JI-2.1947.0048","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0048","url":null,"abstract":"The design of machines for medium-frequency power circuits, increasingly used in industry and in aircraft, demands a knowledge of flux-penetration phenomena as affecting both the iron losses and the utilization of the available iron section. The paper shows how hysteresis influences all important quantities, especially the eddy-current loss, the apparent flux, and the utilization factor. Theoretical expressions for these are, on certain assumptions, rather simply derived and presented in a form convenient for use in laboratories and design offices. Curves are given for this purpose, and the ranges of frequency and thickness indicated over which the influence of hysteresis on the other quantities is pronounced. Systematic collection of test results showing their departure from the theoretical values would assist in elucidating the relation of the discrepancies to the grain structure and the metallurgical history of the sheet.","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"226 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127007689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Parasitic losses in synchronous-machine damper windings","authors":"J. H. Walker","doi":"10.1049/JI-2.1947.0003","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0003","url":null,"abstract":"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.","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130805974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The author's reply to the discussions on “Street lighting”","authors":"E. C. Lennox","doi":"10.1049/JI-2.1947.0025","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0025","url":null,"abstract":"","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"97 21","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120823003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The authors' replies to the discussions on \"Excess-current protection by h.r.c. fuses on medium-voltage circuits\" and \"Excess-current protection by over-current relays on medium-voltage circuits\"","authors":"R. T. Lythall, A. Shreeve, P. Shipton","doi":"10.1049/JI-2.1947.0017","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0017","url":null,"abstract":"","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132839190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Tooth-ripple losses in unwound pole-shoes","authors":"W. J. Gibbs","doi":"10.1049/JI-2.1947.0002","DOIUrl":"https://doi.org/10.1049/JI-2.1947.0002","url":null,"abstract":"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.","PeriodicalId":307627,"journal":{"name":"Journal of the Institution of Electrical Engineers - Part II: Power Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1947-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129640116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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