摘要:

The paper presents a new concept for the predetermination of synchronous-machine stability. The concept is based on the realization of a basic closed-loop pattern for a synchronous generator, which, when established, can be subjected to the frequency-response procedure of the Nyquist stability criterion. The basic closed-loop pattern emerges from the application of small-displacement theory to Park's equations for a synchronous generator. The method is applicable to a machine with or without a voltage regulator, but is more useful in the latter case, and this forms the majority of the applications presented in the paper.It is shown that, as a by-product of the analysis, expressions for the damping in a synchronous machine may be derived. Since this is considered to be of some interest, the influence of some of the more important parameters of the machine and regulator on the damping coefficient is demonstrated.

DOI:10.1049/pi-c.1960.0002

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper deals with theRC-analogue representation of electromagnetic fields involving unidirectional current flow, such as those associated with current-carrying conductors lying in armature slots. The resulting magnetic field is in general 2-dimensional and is fully represented in the analogue. Capacitor current in the latter is directly equivalent to current flow in the corresponding section of the conductor, and the eddy-current loss in a conductor may be calculated from the distribution of current between the several capacitors. Some simple examples illustrate the translation of field boundary conditions into analogue terms.

DOI:10.1049/pi-c.1960.0003

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The force exerted on an iron part in a magnetic field may be calculated by a number of different methods, all of which give equivalent force distributions confined principally to a surface. Seven different methods, giving rise to five different surface force intensities, are shown to result in the same total force. Additional volume force components are obtained and a new expression for the actual distribution of force, consistent with all of the methods of calculation, is derived. A common interpretation of the well-known Maxwell field stresses in iron is shown to be incorrect. When the field is specified numerically the calculation of force in terms of surface integrals has certain advantages over the virtual-work method, and it is shown that simple analytic expressions for force which are usually obtained in this way may be easily derived as surface integrals. Practical applications are considered.

DOI:10.1049/pi-c.1960.0005

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper reviews the various types of electron vacuum tubes employed for amplification and generation at microwave frequencies. Emphasis is placed on principles of operation and on tubes recently developed to give high power output, oscillations at the highest frequencies and low noise factors. The treatment is restricted to conventional tubes in which the output energy is derived from the d.c. input. The subject is interpreted in terms of published work, the text being closely associated with a bibliography which is complete up to the Microwave Valve Convention of May, 1958.After a general introduction, the first part discusses grid-controlled tubes. It is then shown how the interaction of space-charge waves with resonant cavities and slow-wave circuits results in the various forms of drift-space and growing-wave tubes. The second part deals with crossed-field interaction in planar and circular geometry and includes an examination of the magnetron. An account is given of novel methods of generation of submillimetre waves and the usual sources of electrons are described. The third part analyses noise phenomena in oscillators and amplifiers.

DOI:10.1049/pi-c.1960.0007

出版商:IEE    

年代:1960

数据来源: IET

摘要:

An optimum linear filter, in the mean-square-error sense, is no better than the optimum attenuator if there is no dissimilarity between the spectral densities of the signal and the noise. However, non-linear filters can use more statistical information about the signal and noise, so that, although they both possess the same spectral densities, a non-linear filter may be able to introduce a significant improvement in the mean-square error (i.e. it can do better than the optimum attenuator). For this reason the use of a non-linear filter in certain circumstances may well justify the greater difficulties encountered in its optimization and physical realization.The class of filters considered in the paper may be defined by a general expression relating output to input:y(t) =∑r=tR∫0∞ωr(τ)θr[x(t−τ)]dτAn almost routine procedure is proposed whereby the optimum set of weighting functions, ωr(τ), can be determined given either long enough samples of the combined input and the signal or sufficient statistical information about their characteristics. Some worked examples demonstrate that:(a) A significant improvement in mean-square error is possible even under the condition when the signal and noise possess the same spectral densities.(b) The class of non-linear filters under consideration can be optimized unhindered by the need to evaluate difficult integrals.(c) Although the physical complexity of the filter increases rapidly with the value ofR, the mean-square error may converge rapidly to an asymptotic value asRis increased; in one example the performance was found to be within about 5% of the asymptotic value withR= 2.

DOI:10.1049/pi-c.1960.0009

出版商:IEE    

年代:1960

数据来源: IET

摘要:

After a review of the aims and merits of protective devices for low-voltage installations, the joint use of h.r.c. fuses and miniature circuit-breakers is shown to be functional in many installations. The hypothesis that the 0.01 sec fusing current forms a criterion for discrimination is subjected to experimental tests and the statistical nature of discrimination is analysed. Practical conclusions for installation design are drawn, and a new fuse series and various other methods for backing-up miniature circuit-breakers are suggested.

DOI:10.1049/pi-c.1960.0010

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The basic computing element of an electronic analogue computer is the high-gain d.c. amplifier, but in order to overcome its inherent drift some form of auxiliary drift-correcting amplifier is frequently used.The paper describes a silicon diode modulator for use in such drift correctors, and shows that the zero stability which can be achieved is comparable with that given by the conventional relay modulator. It is also shown that the use of the diode circuit results in a number of improvements in the overall drift-corrector performance, such as a higher frequency response and practically unlimited life; the design of such a drift corrector for use with a given d.c. amplifier is described in detail and the resulting performance is assessed.

DOI:10.1049/pi-c.1960.0011

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The properties of the solid conductivity state below 600° K are considered in the present Part. For comparative purposes the conductivity at 420° K is given the title of ‘low-temperature reference conductivity σ420’, and this function is studied in relation to its environment. It is found that σ420increases in almost linear fashion with increase of conditioning temperature and that it also increases with increase of chemical activity of the core metal. At constant temperature σ420is invariant over a wide range of applied voltage and current, and shows a high order of stability with time. Perhaps the most surprising result to emerge is the observed vulnerability of the solid conductivity to low-pressure oxygen attack, even at a temperature as low as 300° K.

DOI:10.1049/pi-c.1960.0012

出版商:IEE    

年代:1960

数据来源: IET

摘要:

When a power transformer is loaded so that it is operating at maximum efficiency the copper losses are equal to the iron losses The ‘efficiency’ is, of course, the ‘power efficiency’, i.e. the ratio of output power to input power. The same condition applies for maximum ‘energy efficiency’ only if the load is constant for the period being considered.With most transformers the load varies considerably over a load cycle and the optimum ratio of copper losses to iron losses calculated on the assumption of constant load for a given period can only be, at least, a rough approximation.The paper suggests a method of obtaining a more accurate optimum ratio in cases where the load variation of the transformer can be estimated in advance. The assumption is made that the copper resistance is constant.

DOI:10.1049/pi-c.1960.0013

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The optimum design of non-uniform transmission-lines for a given bandwidth is discussed, and it is stated that the shorter the non-uniform transmission line the more violently its characteristic impedance varies. The concept of complexity of this characteristic impedance function is introduced and a design method is suggested for minimizing the complexity.Numerical examples are given to illustrate the method, and it is shown that it is possible to design tapers even shorter than the Chebyshev type.The method is capable of further extension.

DOI:10.1049/pi-c.1960.0014

出版商:IEE    

年代:1960

数据来源: IET