摘要:

A synchronous motor, constructed by modifying an induction motor by fitting a permanent magnet inside the squirrel-cage rotor, is very useful for drives where synchronous operation is required or where the drop in speed of an induction motor is too great. The paper presents a theory of operation of this type of motor and suggests an empirical design method. The analysis is based on the 2-axis theory of the salient-pole synchronous motor and shows how the properties of the permanent magnet can be taken into account.The principal difficulty in designing the motor arises from the demagnetizing effect on the magnet of the heavy currents which flow when the motor is started up and synchronized. The analysis consists of two parts. First, the performance characteristics are related to the direct-axis and quadrature-axis characteristics, which show separately the variation of flux and magnetomotive force on each axis. A method is then developed for calculating the axis characteristics from theB/Hcurve of the permanent magnet and the dimensions of the machine. In this way the performance can be predetermined.The method is verified by tests on an existing machine. Finally, two other designs, which could be expected to give improved performance, have been worked out.

DOI:10.1049/pi-a.1962.0141

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper describes, in Part 1, a study of probable long-term requirements of the main transmission system in England and Wales. The possibility of continuing to extend at 275 kV is compared with the alternative of introducing a higher voltage, either 400 or 500 kV, and the reasons for deciding to adopt 400 kV as the next step in transmission voltage are given.The research work associated with the development of overhead lines suitable for operating at 400 kV in England and Wales is described in Part 2 of the paper, while Part 3 gives a summary of the main features of the design of the 400 kV substation equipment, overhead lines and cables which will be used to implement the proposals.

DOI:10.1049/pi-a.1962.0143

出版商:IEE    

年代:1962

数据来源: IET

摘要:

An analytical study by statistical methods is made of the unbalance in l.v. distribution systems caused by unequal loads on the different phases of the supply network. It is shown that the current in the neutral conductor is statistically distributed according to theX2distribution on two degrees of freedom and that the probability distribution of the voltage across the consumer's terminals is closely approximated by the normal distribution. The results confirm the conclusions that have been derived from field data and that have previously been used as the basis for estimating the unbalanced voltage regulation in l.v. distribution systems for new housing estates. Correction factors are given in graphical form, which can be used to correct the balanced regulation for the effects of phase unbalance at different risk levels.

DOI:10.1049/pi-a.1962.0151

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The Safety in Mines Research Establishment, in co-operation with the E.R.A., has made a systematic study of the relative ease of ignition by break-sparks of various flammable gases and vapours, together with an investigation of the basic principles involved. A review of the test methods and of the characteristics of the test apparatus is given, as well as a description of the characteristics of break-sparks and of the relationship between these and the ignition characteristics of the discharges. The circuit parameters affecting the incendivity of break-sparks are also discussed.The principles of gas classification on the bases of minimum igniting current and also of chemical composition are described. It has been possible to adopt the latter method as a result of the steady accumulation of basic data, and this has resulted in the inclusion recently in B.S. 1259 of a very large number of gases and vapours without having to test them individually.

DOI:10.1049/pi-a.1962.0153

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper discusses the influence of statistical considerations on the design of tests intended to lead to an assessment of the explosion risks arising from the normal operation of electrical equipment on aircraft The statistical approach implies that a finite amount of testing cannot establish a nil risk, the amount of testing depends upon the degree of assurance required. It is shown that an apparently ‘reasonable’ degree of assurance leads to an unmanageable amount of test effort if the tests are made under fully simulated service conditions.Test effort can be reduced by orders of magnitude if it is possible to assess separately each of several factors that are simultaneously necessary for an explosion Testing can be further reduced when it is possible to speed up the operation of the unit for test purposes. The proposition that test effort may be reduced by using ‘enhanced’ test conditions is considered. In this Connection, dependence on extrapolation procedures is particularly criticized.It is noted that standardization of enclosures for equipment would much reduce test effort. The advantage in relieving the test situation, of dependence on sealed enclosures that need only mechanical testing is emphasized.

DOI:10.1049/pi-a.1962.0155

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The peak values of alternating breakdown voltages were measured for rod-gaps and 12.5 sphere-gaps; the peak dry-flashover voltages of insulators also were measured. Tests were carried out for sinusoidal voltages and with waves containing third harmonics at different percentages and phase angles. The peak breakdown voltages were found to be sensitive to the instant of occurrence of the voltage peak over the half-cycle. They would increase by about 10%; if the peak occurred at the first quarter rather than the middle of the half-cycle. They would, on the other hand, decrease by about 7% if the voltage peak were retarded to the third quarter of the half-cycle. The harmonic content was found to have rather a small effect on the magnitude of the breakdown voltage if the voltage peak remained at the middle of the half-cycle.

DOI:10.1049/pi-a.1962.0157

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The behaviour of minimum-time-response second-order control system is widely known, and in the paper the philosophy of this type of response is extended to the problem of the control of a third-order drive responding to a step in output displacement.The minimum time response of a system is related to physical limitations of the system in respect of speed, torque (i.e. acceleration), and rate of change of torque. These limitations define the characteristics of the optimum traverse cycles, and relationships are derived that may be used to design a controller for operating a drive in accordance with these cycles. These principles have been used to construct a model incorporating a 3 kW Ward Leonard drive. Satisfactory performance is demonstrated with positive and negative load torques and with a substantial change in load inertia.

DOI:10.1049/pi-a.1962.0160

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper describes some methods of constraining the output of a control system to remain within predetermined limits. No ideal technique has been found, for each method either produces transient overshoots into the forbidden range of output magnitudes or impairs the response in the normal operating region.All systems are non-linear in operation for large input signals. Conventional techniques enable the responses to be evaluated for step and sinusoidal input signals, by means of phase-plane analysis and the describing function.

DOI:10.1049/pi-a.1962.0161

出版商:IEE    

年代:1962

数据来源: IET