摘要:

An account is given of the theoretical basis for the design of coaxial resistors that retain their d.c. resistance, without appreciable reactance, at all frequencies at which coaxial systems are normally used. The main restriction on physical size is governed by the avoidance of supplementary modes of propagation. The design employs a uniform cylindrical film resistor with a critically dimensioned outer conductor, the profile of which has the form of a tractrix. Lead-in cones are designed to avoid discontinuity at the connections with the resistor and the outer conductor. Experimental results show an impedance within 1% of the d.c. resistance, with an extremely small phase angle, at all frequencies up to the highest measured, namely 3 450 Mc/s.

DOI:10.1049/pi-c.1956.0001

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The operation of a Schrage motor at synchronous speed is considered, and on the assumption that the air-gap flux at this speed contains space harmonics, an expression for the torque in terms of flux-axis position is derived. This shows that the torque consists of the main component, which is constant for constant brush separation, and variable components depending on (a) unbalance in the secondary circuits owing to errors in brush-separation angles and/or unequal secondary resistances, and (b) the assumed space harmonics of flux. The variable torque components give rise to superimposed speed oscillations and primary-current hunting, when the average speed is just above or below synchronism.An experimental method of investigating the torque is then given, together with two methods of measuring the harmonic content of the air-gap flux. The latter measurements are used to predict the amount by which the total torque varies with the air-gap flux-axis position at synchronous speed.Possible errors are discussed, and an approximate correction for non-linearity due to the brush-contact effect is derived and applied.Experimental results given for a 2-phase machine show reasonable agreement with the theory.

DOI:10.1049/pi-c.1956.0002

出版商:IEE    

年代:1956

数据来源: IET

摘要:

Voltage and power-angle regulation can be used to improve the steady-state stability of synchronous alternators, whereas speed governors and tie-line power controllers often introduce instability.In the paper, methods of determining the effects of voltage and angle regulation on the steady-state stability limit are discussed, and they are extended to allow for the control of the prime-mover torque by means of governors and power controllers. The machine analysis is based on the general equations for synchronous machines.A complete analysis of actual problems is rather tedious, and a differential analyser has been found most suitable for detailed investigations. Results, as obtained for typical alternators, are presented in the form of stability contour diagrams, which are very convenient for design purposes, since optimum control parameters can be read off directly.

DOI:10.1049/pi-c.1956.0003

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The paper gives results of electric breakdown tests on transformer oil, made with direct and alternating voltages and with impulses of different durations. The dried oil used in these tests was filtered and carefully degassed in a closed test apparatus which incorporated the test cell. The oil treated in this way was tested with uniform and non-uniform electrode configurations, and a number of factors which influence the electric strength of the treated oil were examined. With the electric strength of the treated oil as a reference, the effect on its value was examined when a number of different impurities were added to the treated oil.Finally, a theory of the electric breakdown of this type of liquid is suggested which conforms to the experimental observations reasonably well.

DOI:10.1049/pi-c.1956.0004

出版商:IEE    

年代:1956

数据来源: IET

DOI:10.1049/pi-c.1956.0005

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The use of function generators in electronic analogue computing and simulation greatly extends the range of problems which can be solved by these methods. This paper presents a technique in which diode units are used to approximate to the functions by linear interpolation. It is shown that the method can be extended to deal with a wide class of functions, including multi-variate functions.Analogue multiplication and division are discussed as particular cases of function generators, and formulae for the general function are developed.The results are presented of an experimental generator for sinxin the range − π ≤x≤π, in which the error is about 1 ½% of the maximum output.

DOI:10.1049/pi-c.1956.0006

出版商:IEE    

年代:1956

数据来源: IET

摘要:

A sensitive method of microwave power measurement is described which makes use of the mechanical force exerted by the electromagnetic field on a small vane in a resonant cavity. It is shown that the force on the vane is a simple function of the Q-factor of the cavity, the power absorbed in it and the perturbation of its resonant frequency caused by the vane. The results of a comparison between an experimental wattmeter based on this principle and a water calorimeter are given, and the requirements of a practical instrument are discussed.

DOI:10.1049/pi-c.1956.0007

出版商:IEE    

年代:1956

数据来源: IET

摘要:

The object of the present work is to investigate the correlation existing between the decay time and the delay time of the indicial response on the one hand, and the bandwidth and peak values of the steady-state amplitude response and the slope of the phase response on the other.The analysis is applied to five types of electrical networks and to some general classes of circuits, distinguished by the location of their poles in thep-plane. From these investigations the following results are obtained: (a) By interpolation of all numerical results obtained for the five types of networks, the statistical formulae embracing all of them are found, (b) Formulae giving the functional relationship between the decay time and the ratiof3/f6are derived for each class of circuit considered, (c) The formula for the delay time,tl= [dϕ/dω]ω= 0, is checked for all five networks considered and is found to be valid for multi-stage, but not for single-stage, circuits.

DOI:10.1049/pi-c.1956.0008

出版商:IEE    

年代:1956

数据来源: IET

摘要:

It is well known that the time-constant of a self-saturating transductor is determined mainly by the control winding, increase in the resistance of which will have the effect of reducing the time-constant, but that the time-constant is also influenced by the main winding, so that it is not strictly proportional to the conductivity of the control circuit.The paper deals with a theory for the effect of the main winding on the time-constant, and describes laboratory tests which confirm the theory; its consequences in cases where there is negative feedback from the output voltage are particularly discussed.

DOI:10.1049/pi-c.1956.0009

出版商:IEE    

年代:1956

数据来源: IET

摘要:

An analysis of the behaviour of the single-core, auto-self-excited, transductor element is made for the condition when the control circuit has finite resistance. Consideration is given to control by direct-voltage signal as an introduction to the performance with an alternating-voltage signal of the same frequency as the supply. Factors influencing the output characteristic are examined, and methods of improvement, such as phase shift and special bias arrangements, are discussed.The a.c. control of full-wave transductors and some push-pull circuits with half-wave and full-wave outputs are referred to. The behaviour of a typical push-pull 4-element design is examined experimentally, and its performance when the control is by alternating-voltage signal is compared with that for direct-voltage control.

DOI:10.1049/pi-c.1956.0010

出版商:IEE    

年代:1956

数据来源: IET