摘要:

A relatively new type of motor which has a stationary armature, wound with a number of independent coils, is the subject of the paper. Its coils are connected in parallel to the supply via thyristors, which are used to control the time intervals during which currents are allowed to flow in the coils. The stator is slotless, and its coils are wound to form a ring-type winding. Alternating- or direct-voltage sources can be applied to the armature of the motor. In the machine being discussed, alternating voltage is applied for starting and low speed, and direct voltage for normal running, which, in this case, is from 600 to 3550rev/min. When a direct voltage is applied, induced-e.m.f. commutation is used to cut off the coil thyristors.

DOI:10.1049/piee.1970.0349

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A new technique is presented using principles of multisignal relaying for the synthesis of a universal-type quadrilateral polar characteristic. Themodus operandiconsists in the determination of the phase sequence of a set of voltage phasors and the provision of a trip signal for one sequence while blocking for the other. Two versions, one using ferrite-core logic and another using transistor logic, are described in detail. The former version has the merit of simplicity and has the added advantage of not requiring any d.c. supply. The unit is flexible, as it permits independent control of the characteristic along the resistance and reactance axis through suitable adjustments of replica impedance angles. The maximum operating time is about 20ms for all switching angles, and with faults within 95% of the protected section. The maximum transient overreach is about 8%.

DOI:10.1049/piee.1970.0350

出版商:IEE    

年代:1970

数据来源: IET

摘要:

A description is given of a harmonic-analysis measurement facility designed at the Central Electricity Research Laboratories to statistically analyse harmonic levels on the supply system. As an example of the application of this facility, typical results are given of a statistical analysis of voltage harmonics at selected points on the 275kV Grid system.

DOI:10.1049/piee.1970.0351

出版商:IEE    

年代:1970

数据来源: IET

摘要:

It is shown, by an extension of the optimality condition in the frequency domain, that certain relationships exist between the response of optimal system, the elements of the weighting matrices of the performance index and the optimal feedback matrix. On the basis of these relationships, and using a root-locus procedure, weighting matrices can be chosen which give a desired optimal response, and the corresponding optimal feedback can be calculated. Though general in its nature, as a computational technique it is at present limited to single-input systems. For single-input systems, a relationship between the performance index and the optimal feedback is also established. For the special case of single-input systems, a direct relationship is obtained between the closed-loop poles and the feedback matrix. Although the resulting system may, or may not, be optimal, this relationship constitutes a useful design procedure. An example is given illustrating the technique.

DOI:10.1049/piee.1970.0363

出版商:IEE    

年代:1970

数据来源: IET

摘要:

This paper presents a new method for determining the parameters of a process whose behaviour can be modelled by a linear differential equation with time-varying coefficients in the form of finite-order polynomials. The simplicity of this method lies in the online generation of a set of independent linear time-invariant algebraic equations in the unknown parameters.The development of this method is based on the novel approach of treating the excitation and response signals as distributions, and expanding them in exponentially weighted series of the generalised time derivatives of the impulse distribution. These expansion coefficients are used to form the algebraic equations in the unknown parameters. A practical means of obtaining the expansion coefficients online consists of Poisson filtering the process signals and sampling the filter outputs simultaneously.

DOI:10.1049/piee.1970.0364

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The parameter methods, namely the parameter-plane and the parameter-matrix formulations, were developed to solve high-order multiloop distributed-parameter problems that were too tedious to be solved using the usual classical techniques. Essentially, the methods give graphical plots relating two design parameters and the zeros of the characteristic equation. The paper summarises the solution for several previously obtained cases relating the parameters and coefficients, and generalises the relationship to a completely unrestricted case, using well known function-minimisation methods, such as the conjugate-gradient technique. Moreover, a useful comparison to the generalisedDdecomposition method is made.

DOI:10.1049/piee.1970.0365

出版商:IEE    

年代:1970

数据来源: IET

摘要:

The paper presents a solution to the fundamental algebraic problem: find the necessary and sufficient conditions on the coefficients of a real polynomial II(Ω) so that it is nonnegative, i.e.II(Ω)≥0 for all real ω≥0The solution leads to a unique algebraic criterion for absolute stability, optimality and passivity of dynamic systems, which is an alternative to various analytic frequency criteria developed in modern system theory. The algebraic criterion is superior to the analytic criteria since it avoids any graphical construction and is suitable for machine computations.

DOI:10.1049/piee.1970.0366

出版商:IEE    

年代:1970

数据来源: IET

摘要:

Bode's concepts of return difference and return ratio are shown to play a fundamental role in the analysis of multivariable feedback control systems. Matrix transfer functions are regarded as operators on linear vector spaces over the field of rational functions in the complex variables. The eigenvalues of such operators are identified as characteristic transfer functions. The corresponding characteristic frequency responses provide a simple and natural link between classical single-loop design techniques and multivariable-system feedback theory. These concepts then serve as a unifying thread in a coherent and systematic discussion of multivariable-feedback-system design techniques.

DOI:10.1049/piee.1970.0367

出版商:IEE    

年代:1970

数据来源: IET

摘要:

Following a brief outline of the inverse Nyquist design method as applied to multivariable systems, its application is illustrated by a detailed analysis of the stages involved in the design of a controller for a gas turbine. This leads to a new type of controller which may be regarded as a multivariable version of a classical lead compensator. Comparison with more familiar multivariable design methods shows the inverse Nyquist method to be superior, not only in the controllers it leads to, but also in the information it gives the designer.

DOI:10.1049/piee.1970.0368

出版商:IEE    

年代:1970

数据来源: IET