摘要:

Large superconducting coils, with stored energies from 108J upwards, must be stable and have a predictable performance. This is achieved by combining the superconductor with a good ordinary conductor (substrate) to form a composite and by providing cooling throughout the winding. In addition, large superconducting coils must be protected against overheating and voltage breakdown which might be caused by some failure, notably of the cooling system. We show that the use of an external resistor with a switch is a suitable method of protection and is preferable to the use of a secondary winding. A composite conductor is again the solution, and we show how to determine the minimum quantity of substrate which will satisfy the requirements both of stabilisation and of protection. We conclude that such large superconducting coils can be made stable and be protected.

DOI:10.1049/piee.1968.0101

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper describes an electromagnetic suspension in which use is made ofLCRcircuits to modify the force/distance characteristics between magnetised bodies. The modified characteristic is statically stable, and, although the use of series capacitance introducesQfactor lag and oscillations, it is found by experiment that these can be damped out, giving a considerable advantage in power/weight ratio over the eddy-current method of levitation. It appears that analysis is possible by obtaining a transfer function between force of attraction and position, and an outline of the possible approach is given.

DOI:10.1049/piee.1968.0103

出版商:IEE    

年代:1968

数据来源: IET

摘要:

A theoretical 2-dimensional analysis is made of the end region of a single-load crossconnected m.h.d. generator in which the duct cross-section, fluid properties and magnetic field are uniform, infinitely fine segmentation of the crossconnected electrode system is assumed. With a single load connected between solid electrodes at each end of the generator, the analysis predicts infinitely high current densities and electric fields at the junction of the solid-electrode and crossconnected sections. it is shown that these infinite concentrations can be removed by using grading resistors near the ends, and the design of one arrangement of grading resistors is discussed.

DOI:10.1049/piee.1968.0104

出版商:IEE    

年代:1968

数据来源: IET

摘要:

A simple continuous process is controlled by a digital computer. The process is initially identified and thereafter represented on a digital computer by means of a dynamic model. The optimum response of the model is obtained by adjusting the parameters of the digital controller to minimise a chosen cost function. Once the optimum controller has been determined by methods involving conjugate gradients, as compared to the method of steepest descent, the model is replaced by the actual process, which can then be controlled in an optimum fashion. It is possible for the computer to determine the model of the process and the optimum controller in an uninterrupted manner. The system is subjected to a step demand and a smoothed pseudorandom binary sequence.

DOI:10.1049/piee.1968.0105

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper considers linear distributed-parameter systems described by the diffusion equation. A functional-analysis approach is used to develop a technique for obtaining explicit solutions to the class of optimum-control problems that are reducible to the abstract minimum-norm problem. To illustrate the technique, two specific problems are solved. In both cases, the initial state of the system is specified. In the first problem, it is required to find the spatially distributed control which drives the system to a specified terminal state at a specified terminal time, while minimising a generalised quadratic-performance index. In the second problem, the spatially distributed control is required to bring the system at a specified terminal time to a state which is closest to a specified state, while satisfying an inequality energy constraint.

DOI:10.1049/piee.1968.0106

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The ‘circle criteria’ for giving stability information of linear systems containing one time-varying element are shown to have useful graphical interpretations for design purposes on a parameter-plane diagram. The significance of the parameter-plane approach is that, in a system design, the adjustable parameters of either the time-varying element or the time-invariant subsystem may be selected to satisfy the system stability constraints directly from the diagram. This means that for some design problems the parameter-plane approach is more efficient than the application of the well known complex-plane methods.

DOI:10.1049/piee.1968.0107

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The property of separability of a process with respect tonrandom processes is defined and examples of such a process are given. The equivalent gains of a multidimensional nonlinearity (m.d.n.l.), obtained by Kazakov, are shown to constitute the best linear model of the m.d.n.l. in the Wiener sense if, and only if, each of the inputs is separable with respect to all the inputs. An extended version of Price's theorem is stated and proved, and its use in the determination of the output autocorrelation function for an m.d.n.l. is demonstrated. A series representation of the output autocorrelation function for an m.d.n.l. is also derived. The concepts of d.c. incremental gain and modified nonlinearity are extended to the multidimensional case, and their use in the analysis of closed-loop systems containing an m.d.n.l. is indicated. Finally, the applicability of these results to the general m.d.n.l. withninputs and r outputs is demonstrated.

DOI:10.1049/piee.1968.0108

出版商:IEE    

年代:1968

数据来源: IET

摘要:

In the paper an algorithm is described for solving the problem of secure economic load scheduling on a large power system. The method is an extension of that of Wells, which solves the problem as a linear program by means of the dual simplex algorithm. A dual form of the decomposition principle of Dantzig and Wolfe is used in order to reduce the size of the problem, so that it can be solved efficiently on a computer system. This is correlated with a corresponding decomposition of the power system into autonomous areas, co-ordinated by the specification of recommended boundary transfers and spinning spare capacity. Further levels of decomposition are incorporated in a similar fashion, allowing three or more levels, say, for the CEGB supply system. Although the entire problem can be solved on a single computer, for application to online control a more complex computing system is anticipated.

DOI:10.1049/piee.1968.0110

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper is concerned with some digital-computer programs that were used in an experiment in automatic load dispatching. The problems of economic scheduling of generator outputs and assessment of the security of the supply network are discussed, and the programs used to solve them are described. The programs were adequate for experiments on automatic load dispatching, but experience has shown that they will need to be elaborated for use in a fully operational system. Some areas in which this elaboration will be necessary are listed.

DOI:10.1049/piee.1968.0111

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper assesses the performance of the frequency-control loops of the machine controllers installed in the power stations participating in the automatic-load-scheduling experiment. It first describes the role of these control loops and explains the mechanism of frequency control, and then examines in detail the stability and performance of the machine-controller frequency loops. Included are results of extensive field tests carried out on both individual machines and isolated systems and of analogue-computer simulations. Stability and performance are shown to be closely dependent on the response characteristics of the conventional speed governors, as well as on the controller parameters.

DOI:10.1049/piee.1968.0112

出版商:IEE    

年代:1968

数据来源: IET