摘要:

A noncontact telemetry system using a remote passive transponder in a feedback loop has been developed. The transponder consists of a primary coil tuned to 9 MHz, a secondary coil having a variable resonant frequencyfs≃ 190 k Hz (dependent on a measurand), and a junction diode. Transmitter and receiver coils inductively link to transponder primary and secondary coils, respectively. The transmitter-coil voltage is 4.5 V r.m.s., and consists of a carrier at frequency 9 MHz, amplitude modulated at frequencyfm, variable about 190 kHz. Detection occurs in the transponder so that a signal atfmappears in the secondary and receiver coils. The feedback loop contains a phase-sensitive detector and voltage-controlled oscillator, and operates so as to maintainfm=fsso that the feedback signal (and system output) is always directly related tofsand thus the measurand. The experimental system enables a transponder of volume about 1 cm3to move about in a volume of at least 2000 cm3, with the transponder some 25 cm from transmitter and receiver coils. Depending on its position, the transponder dissipates between 0.25 μW and 10 μW of electrical power. With moderate transponder movements, measurement accuracies of 1% should be possible. Improvements to allow for any transponder orientation, and to provide for multichannel operation, are proposed.

DOI:10.1049/piee.1979.0159

出版商:IEE    

年代:1979

数据来源: IET

摘要:

S.S.B. a.s.k., o.q.a.s.k., q.a.s.k., m.s.k. and q.p.s.k. with rectangular shaping are modelled by a simple baseband system. It is assumed that the symbol shaping in the transmitter is either rectangular or sinusoidal, and that the detector filter is either matched or variously mismatched to the shaping signal. General formulas for the signal and noise variance at the detector output are presented, the assumption being made that the bandlimiting transmitter-receiver filter is causal, with a finite number of simple poles or of the Butterworth type from which the error probability can be computed. The error probability was actually computed assuming the transmitter filter is wideband and the receiver filter is of order 2 or 4 Butterworth. The conclusion is that for a small normalised bandwidth (0.5 ≤B≤ 1.1) the best system has a sinusoidal shaping filter and no detecting filter.

DOI:10.1049/piee.1979.0160

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Because of perceived economic and technical benefits, digital voice techniques and corresponding packet network architectures are receiving considerable attention. In this paper we summarise speech traffic models, followed by a discussion of performance criteria. A queuing model for a link carrying packetised voice is introduced and solved. The results and network implications of this link model are addressed; results on optimal packet length, transient behaviour, and buffer length are presented.

DOI:10.1049/piee.1979.0161

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Hybrid permanent-magnet reluctance motors have to be designed with many performance parameters in mind. The configuration is not a simple one, and some parts of the magnetic circuit operate in the nonlinear regime. The effect of the choice of design dimensions is considered, and the effect on pull-out torque computed as some of the important paramenters are varied. It is seen that some design parameters have a major effect on performance, although others are much less critical.

DOI:10.1049/piee.1979.0162

出版商:IEE    

年代:1979

数据来源: IET

摘要:

A circle diagram is described for the d.c. braking of an idealised linear induction motor with an iron-backed or air-backed conducting secondary. Braking thrust and normal force can be easily predicted from the diagram. Experimental confirmation of the method is described.

DOI:10.1049/piee.1979.0163

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The phase co-ordinate method is applied to the study of some dynamic characteristics of single-cage deep-bar and double-cage induction motors. Particular attention is given to the dynamic run-up characteristics and how they are modified by the effects of saturation, inertia or load, and, for synchronous motors, by field connection. Induction motors are studied further in the complex transient situations arising owing to nonsimultaneous breaker operation, system fault condition, reswitching and plugging operation.

DOI:10.1049/piee.1979.0164

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The representation of magnetic saturation of generators in power system studies is re-examined in the light of new test data obtained on 500 MW and 660 MW units. A new saturation model, of adequate simplicity for use in multi-machine studies, is formulated and checked for accuracy. The parameters for use in the model are obtained firstly from no-load measurements but later in the paper it is shown that the parameters can be obtained from on-load measurements. The primary incentive for the work was to devise a method for the accurate calculation of generator rotor angle when operating at leading power factors. In the event, the model is shown to produce accurate calculation of both rotor angle and excitation requirements over the whole of the normal operating range.

DOI:10.1049/piee.1979.0165

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper describes the modelling of an untransposed transmission line with frequency-dependent parameters, and its implementation in an existing electromagnetic transient program based on the method of Bergeron. Only relatively short lines are used in this paper. To diminish the computation time, it is favourable to calculate the voltages and currents in a modal system; this is only possible if one tolerates certain approximations, which are dependent on the transmission-line geometry.

DOI:10.1049/piee.1979.0166

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper presents an analysis of the single-phase saturated reactor using a mathematical model based on a 2-state switched linear circuit theory. It is shown that the observed incremental fundamental-frequency voltage/current characteristic is not an image of theB/Hcharacteristic of the core, but when saturated corresponds to a reactance that is greater than the leakage reactance of the reactor. This increase is due to the inherent control action of the iron core and is influenced by the harmonic content of the terminal voltage of the saturated reactor. From the theory developed, the saturated reactor is seen to complete its full transient response in half a cycle. Experimental results using 100 VA models of both a saturated reactor and an equivalently controlled thyristor-switched reactor are given to confirm the theory.

DOI:10.1049/piee.1979.0167

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper presents an algorithm for optimising the substation earthing grids with respect to the grid total installation cost, based on digital grid simulation. The optimisation also considers the effects of overlaying the substation area with high-resistivity material and the influence of grid crossconnections.

DOI:10.1049/piee.1979.0168

出版商:IEE    

年代:1979

数据来源: IET