The input admittance of an elemental radiator on a curved surface, e.g. a slot on a cone, plays an important role in the design of conformal arrays. A search through the literature reveals that, at present, there is no reliable theoretical method available for computing this admittance. The objective of this paper is to provide a solution to this problem using a surface-ray approach-within the fra...
The real parts of the invariant zeros of an mx system S (A,B,C) satisfying a partial symmetry condition can be bounded from above and below by the eigenvalues of the symmetric part of A. Where applicable the results provide a simple computational technique for assessing the minimum phase structure of the system.
Trapezoidal rule of integration is used for the computation of impulse-voltage stresses in transformer windings through a companion-network approach. The method is compared with two other methods, one based on eigenvalues and eigenvectors and the other based on series expansion of the state-transition matrix. The method is also verified by comparing it with experimental results.
When the response of the commutating flux is delayed, the appropriate electromotive force for commutation is not induced in the armature winding. The time delay of the commutating pole flux is due to eddy currents induced in the yoke or liners, and results in brush spark. The theory of time delay of the commutating pole flux has been derived by Rudenberg. However, it has been pointed out that the observed value of this time delay is much smaller than the calculation given by Rudenberg's theory. Therefore, the authors have modified Rudenberg's theory, adopting new assumptions concerning the flux distribution in the airgap and considering the effect of fringing flux. The derived theory is compared with experiment and shows a good agreement. Furthermore, to test the influence of a nonmagnetic liner, the cutoff test of the conventional 1700 kW mill motor and the improved one in which a `high resistance nonmagnetic liner? is installed has been conducted. As a result, it was concluded that the nonmagnetic liner plays a more important role in the flux delay than the magnetic liner. It was concluded that this phenomenon cannot be explained using Rudenberg's theory, but, with the authors' theory, it can.
This paper deals with a class of brushless a.c. reluctance machines capable of operating over a wide speed range when fed from a source of constant voltage and frequency. The principle of operation depends upon the exploitation of the properties of a series RLC circuit in which the stator-winding inductance is a function of both current and rotor position. The system is described by nonlinear diff...
Identification of systems which can be represented as a finite sum of factorable Volterra kernals, each composed of individual linear dynamic subsystems, connected in parallel with outputs multiplied in the time domain, is considered. Both a multilevel-testing and a sequential-single-test procedure are derived to isolate each factorable kernel, and algorithms, which provide estimates of the indivi...
The analysis of a step discontinuity of single-mode slab waveguide excited in the dominant mode is presented for both TE- and TM-modes. The problem is formulated by using the mode-matching procedure parallel to that of Marcuse. The solutions for the reflection coefficient, transmitted power and radiated power are then obtained by the application of the residue-calculus technique, which leads to mo...
The development of permanent-magnet generators is reviewed and a novel multistacked form described. This machine is ideally suited to the production of a high airgap field from ceramic magnets, but polymer-bonded rare-earth magnets may also be used to advantage. A damping device can be incorporated to minimise load-angle oscillation. The use of capacitance to improve regulation and increase output...
The paper describes the development of the numerical Fourier transform with exponential sampling. This is called the exponential Fourier transform (e.f.t.). The e.f.t. gives quite a high accuracy and a very long observation time with a small number of samples in comparison with a conventional numerical Fourier transform with equally spaced sampling. Thus, the computational efficiency of the e.f.t. is much higher than the conventional Fourier transform. Various calculated examples using the e.f.t. are given and are compared with the results obtained by the conventional Fourier transform. From the results the superiority of the e.f.t. compared with the conventional Fourier transform becomes clear. The e.f.t. would be very useful to deal with electrical transients with a very wide range of frequency or time.
In a rectifier network, or group of such networks, fed by a 3-phase power supply, if the pulse number p of the rectified voltage is equal to 3 (or a multiple of 3), the primary currents have kp±1-rank harmonics only, k being an integer. In this paper, a general demonstration of this property is given, regardless of whether the load is infinitely inductive or not, and without ever specifying the di...
A new speed-control system suitable for a wound-rotor induction motor is introduced. This system is a combination of two schemes: primary voltage control by means of bias voltage control and Scherbius control. The performance characteristics of the system are obtained and compared for the two types of speed control (new speed control system against hybrid system and Scherbius system). The investig...
The inherent unbalance in a 3-phase linear induction motor (l.i.m.) operating under a voltage-fed mode is accentuated by end effects at high speeds. The voltage-fed operation is analysed by identifying the slip-dependent inductance coefficients corresponding to the positive- and negative-sequence components, and taking into account the stator resistance and leakage reactances. The approach takes c...
The Hopf bifurcation theorem is used by physicists, biologists and others interested in oscillations in systems described by differential equations. This paper presents a version of the theorem applicable directly to feedback systems, using the method of characteristic loci in an interpretation which looks rather like a multiple-loop version of the graphical describing function method. Frequency, ...
The problem of approximate realisation is described and various methods are discussed. A new method is then given which directly identifies the system poles from pulse response data by finding the local minima of a real function of a complex variable. These estimates of the poles are then refined using a new iterative nonlinear least-squares algorithm. Finally, these methods are applied to a `seis...
Connection of the Dinorwic pumped storage station in Snowdonia to the 400 kV supergrid is to be made by two 400 kV cable circuits rather than by overhead lines because of the outstanding natural beauty of the area. The cables have 2500 mm2 copper conductors, oil-filled paper insulation and aluminium sheaths and will be cooled by circulating water in high density polyethylene pipes laid with the ca...
The paper reports the results of an experimental investigation into the dielectric-breakdown behaviour of super-critical helium, in the range from 4.2 to 30 K and 0.4 to 1.5 MPa under d.c., a.c. and standard impulse voltages, to assist the development of superconducting power cables. At helium densities above 80 kg m−3, the uniform-field breakdown voltage for d.c. or a.c. is about 55 MV m−1 at 0.8 MPa and has a slight pressure dependence. In nonuniform fields, the breakdown voltage with a negative electrode is considerably increased by corona stabilisation in the density range from 30 to 83 kg m−3.
