摘要:

The maximum possible increase in gain/rise-time for a 2-terminal network with shunt capacitance is shown to be 2.75 compared with the parallelRCcase; the overall gain/rise-time figure for a cascade ofnsuch stages is also deduced. As such networks would have a large amount of overshoot, those having a monotonic response to a stepfunction current drive are next considered. Improvement in figure of merit is shown to be greatest with complex poles and zeros, and the case of three poles, two of which are conjugate complex, is discussed in some detail. Finally, modifications are made to a network with three poles having a monotonic response so as to produce improved risetime at the expense of a small amount of overshoot; e.g. a figure of merit of 1.90 can be obtained with 1% overshoot.

DOI:10.1049/pi-c.1957.0028

出版商:IEE    

年代:1957

数据来源: IET

摘要:

With the aid of methods previously developed, an approximate expression is obtained for the difference from unity of the transmission coefficient for plane waves at normal incidence of a large aperture of rather general form in a plane perfectly-conducting screen. The coefficient is expressed in the form of one or more line integrals taken around all (or part) of the aperture rim. These may be evaluated analytically in certain cases, e.g. a circular or elliptical aperture. In the former case the result agrees with that derived elsewhere; the ellipse is considered in some detail in the present paper, and the transmission coefficient is evaluated for a range of eccentricities. The results appear to be in qualitative agreement with the limited experimental data available.

DOI:10.1049/pi-c.1957.0029

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper is divided into three parts, concerned respectively with the measurement of cathode emission and resistance and with the relationship between these two parameters and the mutual conductance of a pentode receiving valve.Part 1 describes a method of extrapolating the zero-field total cathode emission at normal operating temperatures from the low-temperature emission measurement. It is shown that the final result is independent of contact-potential variations or potential drops across cathode, interface or collector films. The cathode work-function can also be derived from the extrapolation.The inadequacies of existing methods of measuring cathode resistance in normal valves are considered in Part 2, which examines the possibility of substituting an empirical relation between emission and resistance whereby the average cathode resistance for a batch of valves may be quickly computed from the average cathode emission.In Part 3 are devised relationships between the state of the cathode and mutual conductance of the valve which are based on theory and experiment. These form models which may be compared with the life-test measurements of mutual conductance and low-temperature total emission. It is found that the model which accords best with the life-test results is that which employs the concept of the cathode state being a function, not of emission alone, but of emission and resistance together.In reaching this conclusion it is apparent that the validity of the comparison between the models and the life-test results must stand or fall by whether the assumptions which must be made in connection with the cathode work-function can be justified. With one exception it does, in fact, prove possible to justify all the assumptions required: the exception indicates, however, that the relationships which form the acceptable model have a limited, not a general, application.

DOI:10.1049/pi-c.1957.0030

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Various equivalent circuits used, or suggested, for transformers and induction motors are examined by considering them as 4-terminal networks, and determining the corresponding general circuit constants by matrix methods. The information obtainable from tests is discussed, and the use of the 4-terminal network is proposed as considerable generality is achieved by this approach.

DOI:10.1049/pi-c.1957.0031

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper presents what is believed to be a new theorem in electrostatics, showing that the direct capacitance of a very general type of cylindrical 3-terminal capacitor is a constant, namely (logε2)/4π2.The presentation and proof of this theorem is followed by a detailed analysis of a cylindrical 3-terminal capacitor of rectangular cross-section, in which the effects of various practical limitations are evaluated in quantitative terms. The results of similar analyses of cylindrical 3-terminal capacitors of other cross-sections are stated.As a consequence of this work, it appears that such cylindrical 3-terminal capacitors are extremely attractive as precise calculable standards of capacitance, only one precision length measurement being necessary to enable their capacitance to be computed to a high order of accuracy.

DOI:10.1049/pi-c.1957.0032

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Reliable equations of performance for the Schrage motor are deduced in terms of the angle between the stator and the rotor magnetomotive force waves, resulting in an original treatment. The expressions for torque, slip and current in terms of this angle are derived and are discussed with the aid of graphs and locus diagrams.

DOI:10.1049/pi-c.1957.0033

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper analyses five basic types of chopper circuit suitable for converting low-level direct voltages to alternating voltages. Three of them are capacitance coupled and two are transformer coupled; all have resistive loads.Both transformer-coupled circuits have make-before-break (overlap) contact action and incorporate a stopper resistor. If the overlap is small, this arrangement provides input resistances which approach those of the equivalent buffered underlap circuits, together with several other advantages.Expressions are derived for gain, input resistance and optimum stopper resistance in terms of the component values.

DOI:10.1049/pi-c.1957.0034

出版商:IEE    

年代:1957

数据来源: IET

摘要:

It is shown that the stray loss in induction motors, at fractional slips greater than about 0.25, is almost entirely due to tooth ripple in the zigzag leakage flux. The stray loss is large; it can double the torque at a slip of 2.0 and can lead to serious errors when calculating accelerating and braking performance. In the normal operating range, i.e. slip less than 0.05, although the stray loss is much lower it is still appreciable, and the component associated with tooth ripple in the main flux is of importance. Experimental evidence, both from actual machines and from high-frequency loss in samples of laminations, indicates that the zigzag leakage flux component of the loss is approximately proportional to (speed)1.6and (current)1.9, and the results of the American Standard reverse-rotation test extrapolated according to this law are sufficient, together with the no-load stray loss, to predict the total stray loss over the whole practicable speed range.A simple method for calculating the stray loss is given and its limitations are indicated. Calculated values of the loss are compared with the measured losses, but no definite conclusions as to the accuracy of the calculations can be drawn until more is known of the highfrequency loss in machine laminations.

DOI:10.1049/pi-c.1957.0035

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Tensor analysis is used to develop a comprehensive theory of the stator-fed 3-phase shunt commutator motor. Before proceeding with the general analysis, the simple case of a machine where all the phase shift between the secondary standstill induced voltage and the secondary impressed voltage is either in the motor or the regulator is considered. From the equations of performance of the simple machine, the existing equivalent circuit proposed by Coulthard is derived. The limitations of this circuit are discussed and better circuits are proposed. For the general analysis, the machine has an auxiliary winding on the stator displaced from the main winding for power-factor improvement, a shift of the brushes from the neutral position, and a biased double regulator with completely dissimilar-component single regulators for speed and power-factor control. An equivalent circuit for the general machine is proposed and a method of measuring its parameters is indicated. Certain modifications to the theory to overcome inherent limitations are discussed.

DOI:10.1049/pi-c.1957.0036

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper is the first of a series dealing experimentally with various aspects of the conductivity of oxide cathodes. The present Part starts with a brief survey of existing knowledge and then proceeds to examine the practical circumstances under which a non-uniformity of potential gradient can arise across the matrix under a modest continuous current loading. Using active-nickel cores to enclose a rectangular slab of barium-strontium oxide, it is found by probe experiments that nonuniformity of potential gradient occurs only in the presence of residual gas, and that the gradient tends to increase in those parts of the matrix likely to accumulate negative ions.

DOI:10.1049/pi-c.1957.0037

出版商:IEE    

年代:1957

数据来源: IET