DOI:10.1049/pi-b-2.1962.0036

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0037

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper describes certain properties of manganese-zinc ferrite cores used in inductor coils. In particular, the stability characteristics which appear to be substantially different from those of iron or alloy dust cores are examined. It is pointed out that the permeability variations are due to several external causes. Only the principal features of these phenomena may be given because of the large quality dispersion of ferrites.Owing to its very reduced losses the manganese-zinc ferrite is the best material for low-induction coils used in the zero to some hundred kilocycles per second frequency range. However, its use requires very accurate knowledge of the different aspects of the stability phenomenon.Some measurement results illustrate the typical behaviour of essential ferrite characteristics.

DOI:10.1049/pi-b-2.1962.0039

出版商:IEE    

年代:1962

数据来源: IET

摘要:

New techniques for obtaining either a perfectly sinusoidal magnetizing force or flux density in magnetic sheet steel at high flux densities have enabled more reliable performance characteristics to be obtained, which can be extrapolated with greater confidence to still higher densities. The test results for a variety of specimens cover the frequency range 0.2–2.4kc/s, and up to a flux density of 20kG in the case of Permendur (49% cobalt, 49% iron, 2% vanadium), or 16kG for a 0.3% silicon-iron. It is shown that the iron losses for the alternative sinusoidal conditions of magnetization are not very different, except for densities above about 10kG at the lower frequencies. The a.c. permeability decreases appreciably with increase of frequency at medium densities, but at high densities it becomes equal to the d.c. permeability at all frequencies; the higher the frequency, the higher is the density at which the a.c. and d.c. permeability become identical.Further results of practical interest are that thin laminations of high silicon content require to be specially annealed to maintain a lower loss at high densities than thin laminations of low silicon content; flux distortion in the individual laminations substantially increases the loss of a packet of laminations above that obtained when the flux in each lamination is constrained to be sinusoidal; an appreciable error is involved in assuming that test results on a single strip are representative of a packet from the same sheet; the loss exponent of frequency can vary appreciably at saturation densities, but is otherwise virtually constant, whilst the loss exponent of flux density can vary from about 1.6 to 3.

DOI:10.1049/pi-b-2.1962.0040

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Electromagnetic relays deteriorate in service. Part of this deterioration is due to ageing of the iron employed in the magnetic circuit, and, in particular, to the use of annealing atmospheres, such as cracked ammonia, which contain nitrogen. If such atmospheres are unavoidable, then, for most practical purposes, ageing can be eliminated by the use of irons containing about 0.1 % of aluminium. Silicon, in the iron initially or available in the furnace lining, increases nitrogen ageing. The best properties are obtained by annealing in a furnace lined with alumina, in an atmosphere of wet hydrogen and with an iron free from additions. The properties obtained by treatments at high temperatures are not always unique: they can sometimes be obtained by more prolonged treatment at a lower temperature. Nitrogen-aged piece-parts can be salvaged and restored to a condition better than new by reannealing in hydrogen.The magnetic circuit of a relay must be able to lift and to release its springset load when needed. The first requirement depends on the normal magnetization curve, and the second on the coercive force. Nevertheless, relays are manufactured without sufficient consideration of the properties of the iron necessary for the performance of specific functions. An experimental technique has been devised for the retrospective determination of the requisite properties. The significance of the normal magnetization curve is ascertained by studying the alteration in load-lifting ability as the (field-dependent) permeability is systematically degraded, starting with a ‘better-than-necessary’ material. This is done by reducing the cross-section of the magnetic circuit in such a way that the configuration of leakage paths is not altered. The relation between release m.m.f. and coercive force is approached by first considering the change to be expected in the hysteresis loop for a uniform ring when a gap is introduced, and then examining the relationship between this changed loop and the release of a uniform and of a non-uniform relay.

DOI:10.1049/pi-b-2.1962.0041

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A simple saturable inductor circuit operated from a sinusoidal source is shown to be a useful test circuit for ferromagnetic cores. The pulse-field/pulse-duration characteristic of the material, which is necessary for the design of devices that depend upon reactance switching, can be ascertained. The pulse-field curves enable the probable time the flux in a lamination takes to attain a specific value (the ‘core time’) to be determined. The circuit is shown to have uses for grading batches of cores and for indicating interlamination faults.

DOI:10.1049/pi-b-2.1962.0042

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper surveys the properties and applications of present-day ferrites intended for use as cores for high-quality inductors and transformers in carrier telephony and similar equipment. In considering the properties, emphasis is placed on the significance of the various parameters used to define ferrite performance. Typical values of these properties are tabulated.Considering the application of ferrites to high-quality inductors, the basic requirements are stated. The realization of these requirements is then discussed, starting with an analysis of the effect of the geometric proportions of the core on its electrical performance and continuing with the design of adjusting mechanisms and the means of assembly. Emphasis is placed on the attainment of the maximum stability of inductance. A similar treatment is given for the application to broadband transformers. It is shown that for bandwidths extending up to 10Mc/s the pot-core shape is suitable, while for bandwidths up to several hundred megacycles per second small, specially designed bead-like cores give very good performance.The paper concludes with a number of graphs showing the performance of typical inductors and transformers using the ferrite cores described.

DOI:10.1049/pi-b-2.1962.0043

出版商:IEE    

年代:1962

数据来源: IET

摘要:

In the mangnese-zinc-ferrous ferrite system (Mnx−yZnyFe3−xO4), which is of considerable technical importance, the magnetocrystalline anisotropy cannot be measured directly because ferrite single crystals containing zinc cannot be produced. It is shown in the paper that the sign and, to some extent, the magnitude of the first-order anisotropy constant,K1can be determined by measuring the magnetostriction of polycrystalline samples as a function of the applied field. This is possible if the magnetostriction constants λ100and λ111have different signs, which is the case in the above system. The result is that in some of the compositions the anisotropy constantK1passes through zero at around room temperature. This explains the occurrence of a secondary peak in the permeability/temperature curve of these ferrites. As the saturation magnetostriction in the same composition is very small, this represents the oxidic analogue of Permalloy.

DOI:10.1049/pi-b-2.1962.0044

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper is in two parts. The first deals with potted or encapsulated circuits and the second with printed wiring and, to some extent, with printed circuits.The present status of potted-circuit constructions and materials is considered, together with the evaluated properties of recently introduced resin systems which have increased heat resistance and more stable electrical properties. The mechanism of failure and remedies re discussed.Developments of printed wiring and printed circuits are compared, and details given of currently available techniques. Materials for both forms of construction are discussed in detail and their physical properties evaluated over a wide range of temperatures and climatic conditions. New low-loss materials are compared with established ones in respect of dielectric properties when wet or dry.There is a shortage of ‘Service’-quality components for printed wiring. Some guidance is given to designers of such components.

DOI:10.1049/pi-b-2.1962.0046

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper reviews briefly some of the characteristics of epoxy-resin systems that are of importance in their application to electrical components by encapsulation, impregnating, laminating, etc. The characteristic properties of these materials are those peculiar to their processing, i.e. low shrinkage and absence of volatile matter on cure. Characteristics important in their application, such as pot life, viscosity, exotherm and shrinkage, are therefore discussed. Some aspects of their electrical and mechanical properties are also discussed, and, though a detailed description of new material is outside the scope of the paper, present and future trends are briefly mentioned.

DOI:10.1049/pi-b-2.1962.0047

出版商:IEE    

年代:1962

数据来源: IET