摘要:

The paper describes how the phase-mixing techniques which have previously been applied to 3phase operation may be extended for use in single-phase machines. A description is given of the operation of the previous 3phase versions when single-phase connected, and a subsequent analysis shows how windings which are harmonic-free at both speeds may be formed.The material is supported by some practical tests in which an example of the new two-speed windings is compared with a single-speed winding in a similar frame.

DOI:10.1049/piee.1965.0194

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The behaviour of a test span, artificially excited into transverse vibration, is studied. The decay mechanism is particularly analysed. It is shown that the decay is of the form of a step curve. The phenomenon is found to appear markedly in highly damped spans, but may be easily overlooked if the damping is small. Damping measurements in a laboratory test span by using the decay method are discussed. It is shown that the commonly used logarithmic decrement does not give significant information on the performance of a vibration damper. From the equations given in the paper, it is possible, from decay measurements, to calculate the power consumption which is recommended as a measure of damper efficiency.

DOI:10.1049/piee.1965.0195

出版商:IEE    

年代:1965

数据来源: IET

DOI:10.1049/piee.1965.0196

出版商:IEE    

年代:1965

数据来源: IET

DOI:10.1049/piee.1965.0197

出版商:IEE    

年代:1965

数据来源: IET

摘要:

An instrument is described which can measure strains of 10−5within ±5% over a distance of 2mm. The method is based on optical-lever amplification of the movement due to strain. A special multiple-beam interferometer is used for absolute determination of an internal secondary calibration. The latter is used during measurements of strain to make the instrument effectively a ‘null’ device.

DOI:10.1049/piee.1965.0200

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The paper describes a method of constructing a general form of nonlinear filter in a digital computer. The filter is easily realised and optimised, and the technique provides for the gathering of the necessary statistical data. The memory part of the filter is based on a sampled-data Laguerre filter chain, which is particularly convenient in the expansion of nonlinear operators. The filter memory can be readily adjusted and auxiliary processing can be included for this purpose. An important relationship between product averages of linear filter outputs is described which is used to give economies in computation. The paper ends with the description of some results obtained in the solution of a nonlinear identification problem.

DOI:10.1049/piee.1965.0201

出版商:IEE    

年代:1965

数据来源: IET

摘要:

When a digital computer acts as the compensating element of a sampled-data feedback system, the system performance is degenerated by the computational errors inherent in the finite-word-length machine.The statistical analysis presented in this paper enables the increase in the mean-square system error due to quantisation and computer roundoff errors to be assessed for a closed-loop linear sampled-data system. In fact, the loss in overall performance can be determined by slide-rule calculation for all computer word lengths. A further advantage of the present approach over previous work is that the necessary computations are performed on the conventional block diagram of the system, rather than its matrix equivalent. One application of the analysis is to specify the precision required in the digital compensator and peripheral equipment for consistency with the overall accuracy demanded of the closed-loop system. It also enables the selection of the programming technique which requires the shortest computer word length for this accuracy.As a means of verifying the analysis, the performance of two different digital compensators for a practical system are each compared with a counterpart having negligible quantisation and roundoff errors.

DOI:10.1049/piee.1965.0202

出版商:IEE    

年代:1965

数据来源: IET

摘要:

For many years, controversy has raged about the best method of analysing the behaviour of induction-type instruments. On the one hand, the idea of a travelling field, appropriate to the induction motor, has been advanced for these instruments without much conviction. On the other hand, the technique of superimposing forces of interaction between one component of the magnetic field and the induced current of the other has been shown to offer a reasonable explanation. In view of the development of this type of instrument for radio measurements, consideration has been given in this paper to the basic conception of absorbing the momentum of a travelling field as a means of producing a mechanical force proportional to the power dissipated, and also to the application of this idea in examining the operation of induction-type instruments and motors. A simple theory which appears to be satisfactory over a wide range of frequencies emerges from this approach.

DOI:10.1049/piee.1965.0203

出版商:IEE    

年代:1965

数据来源: IET

摘要:

The spatial and temporal growth of discharge channels about a point electrode in Perspex has been investigated using impulse voltages. The channels develop substantially at random. Evidence is produced showing that they consist of hollow nonconducting tubes in which a discharge must be struck before extension can occur. The discharge within a channel acts as a conducting extension of the point electrode, and further development occurs by intrinsic breakdown of the material at the end of the channel. The process is believed to be caused by avalanche formation, and material is evaporated until the rise in pressure of the gas within the ignited channel causes the discharge to be extinguished.

DOI:10.1049/piee.1965.0204

出版商:IEE    

年代:1965

数据来源: IET

摘要:

Various shapes of test sample have been recommended for determining the electric strength of ceramics. The form described by the British Standards Institution (BS 1598: 1949) for a proof test for electric strength would normally be chosen, but this type always fails by surface flashover rather than by puncture through the material. It was therefore decided to compare the electric-strength values obtained from five sample shapes (including a thinner version of the BS sample), all prepared from one batch of h.v. porcelain, produced by the same forming process and fired together. The thickness of the porcelain, the surface finish and the electrode material were varied, but other factors influencing the results were standardised. All samples were inspected for faults visually, by a fluorescent-penetrant method under ultraviolet light, and in some cases by X radiography. The fluorescent-penetrant method was very quick and easily applied, and more successful in detecting flaws than X ray inspection.On the bases of the electric-strength results, their consistencies of determined values, and the ease of manufacture and test procedure, an 80mm-diameter disc with a spherical depression in one face, using fired-on silver electrodes on a ground surface, was found to be most satisfactory.

DOI:10.1049/piee.1965.0205

出版商:IEE    

年代:1965

数据来源: IET