摘要:

The paper deals mainly with developments in meter-testing methods which use a watt-hour meter as the standard of reference.A brief survey is included of methods, developed during the last forty years, in which some form of stroboscope has been included, and it is shown that such methods cannot be used for light-load testing owing to the fact that most meters are subject to cyclic variations.Particulars are given of recently devised schemes which incorporate a stroboscope for the higher loads and some other form of testing for the light loads.A description is then given of a new type of meter-testing unit which uses revolving optical compensators to view the disc of a meter under test, in order to compare its speed with that of a substandard meter.An image of the disc marks is obtained which is very similar to a stroboscopic image, but with theimportant difference that cyclic variations do not prevent its use for light-load testing.The new unit can therefore be used for testing meters at all loads from 1/20th to full load, and, as facilities are provided for testing meters having different constants, it is particularly suitable for use in supply authorities' test rooms dealing with different makes of meters, so that its application in this respect is considered in some detail.

DOI:10.1049/pi-2.1950.0051

出版商:IEE    

年代:1950

数据来源: IET

摘要:

Various experiments on the magnetic losses in sheet steel at power frequencies and flux densities are described and their interpretation is discussed. It is concluded that an important fraction of the total loss in low-loss sheet cannot be accounted for by the normal hysteresis and eddy-current mechanisms, or by modifications of the latter to allow for non-uniformity of the permeability. This extra loss seems to be due to the finite velocity of domain wall movements, but it is not clear what mechanism limits this velocity; microscopic eddy currents induced by the wall movement are suggested as a possible cause.

DOI:10.1049/pi-2.1950.0059

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The considerable effect of metallurgical factors on magnetic properties is illustrated by reference to untreated and fully processed nickel-iron and silicon-iron alloys. The factors considered are composition, i.e. major constituents and heterogeneity, purity or differences in ultimate composition, non-metallic inclusions, strain content, structural orientation, grain size andgrain shape, lattice ordering, magnetic domain orientation, and surface conditions and dimensionaleffects. These are denned and their incidence and control in manufacture discussed with particularreference to their effect on magnetic properties. The influence of the above factors on the magnetic properties, saturation intensity, maximum permeability or permeability at the knee of theB/Hcurve, initial permeability or threshold magnetization, d.c. hysteresis loop, particularly coercivity and remanence, total loss under a.c. magnetization at power frequencies, permeability and loss under a.c. magnetization at high frequencies is considered. The fact that they affect the various magnetic properties in different ways so that production methods have to be adjusted accordingly is emphasized.

DOI:10.1049/pi-2.1950.0063

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The development of systems for the transmission of telegraphy, telephony, music and television over lines has made increasingly exacting demands on magnetic materials and cores for transformers. Published data appropriate to the frequencies and inductions usual in line communication are inadequate and largely unreliable as a basis for design; moreover, the characteristics of some materials vary considerably from batch to batch, and with difficult designs this leads to excessive factory rejections.The paper first sets out the theoretical performance for homogeneous magnetic material at very lowinductions and then compares this with test results on typical specimens of materials and cores; most of the data, unfortunately, are not statistical. Results are first given for the initial permeability and eddy-current losses of single ring stampings, and the effects of stacking are examined. Corresponding measurements follow on single turns of typical strip and on spiral cores wound with strip down to 0.0006 in thick; this leads to an investigation of inter-laminar insulation and the effect of cutting to form C-type cores; measurements on some flat laminations are then given. Finally, some typical measured values of hysteresis coefficients and residual loss coefficients are given for the materials concerned.

DOI:10.1049/pi-2.1950.0064

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The paper is supplementary to a previous paper by the author and describes in greaterdetail some aspects of work on the measurement of pulse magnetization characteristics of core materials. Methods and techniques of measurement in the range of pulse durations 0.1–5 microsec, are discussed and a description is given of apparatus and some measuring components which were used incarrying out tests on three relevant core materials.The materials are Radiometal, Rhometal and Mumetal in carefully prepared samples wound from rolledstrip having thicknesses of 0.001–0.010 in. Pulse permeability and loss characteristics for severalpulse durations and values of d.c. polarizing field are shown on curves. The effects of these variables on pulse performance are discussed.A conception of the mechanism of pulse magnetization is described and a method derived for determining analytically the theoretical magnitude of eddy currents and losses for any form of pulse which can be represented by a finite number of linear voltage changes.Results obtained by this methodare compared with practical values.

DOI:10.1049/pi-2.1950.0068

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The fundamental considerations involved in defining the incremental magnetic properties of a material are briefly reviewed, and methods of measuring the properties are described. Measured values at 50 c/s and 800 c/s for the various grades of hot-rolled silicon-iron in common use are tabulated. These measurements were obtained on samples representing the best and the worst (as judged by total power loss at 50 c/s and magnetic flux density of 10 000 and 13 000 gauss) for each grade of material, specially selected from production by the manufacturer.It is shown that the apparent reluctivity of a magnetic circuit, with an air-gap which is optimum for the particular conditions of incremental magnetization, can be related to the apparent polarizing magnetizing force by an empirical equation. This equation is sufficiently accurate for most practical applications, and its use enables a purely analytical method of design of air-gapped smoothing chokes to be evolved. Formulae are developed for designs where the polarizing current and incremental inductance, together with either the d.c. voltage drop or the temperature rise, are specified. Typical values of design parameters used in actual manufactured chokes are given.For comparison, a small number of measurements of incremental properties of two grades of nickel-iron alloys are included in an Appendix.

DOI:10.1049/pi-2.1950.0069

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The paper stresses the need for the development of a standardized commercial method of iron loss measurement at audio frequencies. To assist such a development, the use of a miniaturereproduction of the standard Lloyd-Fisher square is investigated. In comparing results obtained onthe miniature square with those obtained on the standard square, it is found that the hardening effect near the edges of the material due to cutting, is increased and may amount to 5% on the totalloss. Nevertheless, results obtained on the miniature square are probably more representative of values obtained in the practical utilization of sheet metal at audio frequencies.Since the proportionate mass of the overlapping portion in the magnetic square is quite appreciable, its effect is considered in some detail. It is shown that the relation given in B.S. 601:1935, between the loss per unit mass and the total loss measured on the standard square at power frequencies, is applicable to the miniature square at power and higher frequencies.A comparison of loss and permeability measurements on the miniature-square and ring samples demonstrates that the problem of satisfactory sampling becomes more important when test results are required at the low inductions associated with higher-frequency operation.

DOI:10.1049/pi-2.1950.0070

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The paper describes the application of an a.c./d.c. null wattmeter method of iron testing to routine work. The wattmeter circuit is incorporated with computing networks so arranged that the work of the operator is confined to the insertion of basic data and the establishment of a series of four null balances. Use is made of an a.c. peak fluxmeter in establishing the conditionsof test, and compensation is made automatically for circuit losses and air-flux corrections. The method of setting up and of calibration is briefly described.

DOI:10.1049/pi-2.1950.0071

出版商:IEE    

年代:1950

数据来源: IET

摘要:

Powders of iron or iron-nickel alloys can be made either mechanically or chemically. The particles are then insulated and pressed into cores; high-permeability cores must be annealed after pressing. The permeability of the core depends mainly on the effectiveness of packing of theparticles.Various systems of expressing the electrical losses are in use: Table 1 gives conversion factors. In laboratory work, bridges and a Q-meter technique can be used to measure the permeability and losses; for control of core production, a permeameter is useful as well as the bridges.Table 4 gives data for various materials, both commercial and experimental, including some ferrites; and Figs. 4 and 5 show that, in typical inductors, the losses in the windings may exceed the losses in the cores.

DOI:10.1049/pi-2.1950.0075

出版商:IEE    

年代:1950

数据来源: IET

摘要:

In Section 1.1 it is argued that ferromagnetic materials with a high resistivity are of considerable practical importance. In Section 1.2 the electric and magnetic properties of ferrite materials at various frequencies are discussed. In Section 1.3 an account is given of the physicochemical background of the properties of ferrites. In Section 1.4 the manufacture is dealt with and the important possibilities for application of different ferrite materials are briefly reviewed. In the following Sections 2.1–2.5 the experimental methods are described which are used for themeasurements of the electric and magnetic properties of the materials. Section 2.2 deals with a bridge used at frequencies between 1 and 100 kc/s. Sections 2.3 and 2.4 contain a description of themethods used for measurements at frequencies up to 500 Mc/s, while Section 2.5 deals with experiments in the microwave region.

DOI:10.1049/pi-2.1950.0076

出版商:IEE    

年代:1950

数据来源: IET