摘要:

This paper describes inductive interference effects, which exist when track based cables are used for track-to-train speed commands in a railway system, which also uses jointless track circuits for train detection. It is shown that spurious speed commands (ghost signals) can be transmitted to trains not intended to receive the original message, and that in some circumstances this could be dangerous. The paper is based upon theoretical and practical investigation undertaken for the new signalling system for the Island Line extension of the Hong Kong Mass Transit Railway. The paper demonstrates that providing appropriate design criteria are adopted, it is practicable to introduce jointless track circuits, together with tightly coupled track-based conductor loops, to a railway which originally used jointed low-frequency track circuits for train detection, together with track-to-train speed commands using the rails as a transmission path.

DOI:10.1049/ip-b.1988.0007

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The connection of power converter and other nonlinear loads to the electrical power system results in other system components being subject to voltage waveform distortion. In order to predict the resultant heating and harmonic current flows, it is necessary to have fairly accurate models for components such as synchronous machinery. The paper presents a theoretical and experimental study into the electrical behaviour of synchronous machines when subjected to harmonic voltage disturbance at the terminals. It is shown that the time-varying nature of the machine inductances results in current flow at both the applied and at an associated harmonic frequency. Consequently, it is inadequate to model the machinery by a pure reactance at each harmonic frequency.

DOI:10.1049/ip-b.1988.0008

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Optimal PWM switching strategies are presented for the current-source inverter (CSI) induction motor drive. These optimal PWM strategies are designed with the objective of improving the quality of the rotational motion of the drive at low operating speeds, thereby extending the viable range of operation and application of CSI drives. Optimal PWM switching strategies designed to minimise rotor speed ripple and rotor position error are presented, based on both 1/4-wave and 1/2-wave symmetric PWM stator current waveforms, and their superiority demonstrated using both experimental and computed CSI drive performance characteristics. It is shown that 1/2-wave symmetric PWM strategies designed to minimise rotor position error are superior to all previously developed PWM strategies, in terms of producing smooth rotor motion and reduced mechanical resonances, during low speed operation of the CSI drive. In contrast to previously developed CSI PWM strategies based on harmonic elimination/minimisation techniques, which are essentially open-loop strategies, it is shown that all the optimal PWM strategies are dependent upon motor operating conditions and are therefore closed-loop strategies.

DOI:10.1049/ip-b.1988.0009

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Currently accepted definitions of power components are reviewed, and their disadvantages are analysed. New definitions of active, reactive, distortion, and apparent power are discussed. It is attempted to find a clear physical interpretation, and to formulate this for each power component in systems with sinusoidal and/or nonsinusoidal voltage and current. Formulas for the straightforward calculation of each power component are obtained. It is shown that (a) distortion power, as defined here consists of both active and reactive terms (b) apparent power in a nonsinusoidal system must be represented as a many-dimensional vector, and not as a vector of three dimensions as is generally accepted today. Examples are given to illustrate the application of the developed theory.

DOI:10.1049/ip-b.1988.0010

出版商:IEE    

年代:1988

数据来源: IET

摘要:

There has been a serious problem of current out-of-balance in 12-pulse rectifiers between two 6-pulse groups. This has become particularly pronounced with semiconductor rectifiers where 12-pulse operation is obtained by two phase-displaced 3-phase bridge rectifier circuits operating in parallel. A current equalising transformer (CET) was introduced to overcome the problem. A new simpler variation of this has more recently been introduced and the paper describes this new variation and includes more complete and exact design current and voltage relationships than have previously been published.

DOI:10.1049/ip-b.1988.0011

出版商:IEE    

年代:1988

数据来源: IET

摘要:

This paper describes a method of determination of reverse recovery current parameters of the thyristor turnoff model, namely, the peak reverse recovery current and its decay time constant. The parameters are determined from a set of recovered charge curves, and another set of reverse energy loss curves, usually given in the manufacturer's data sheet so that the curves may be fitted over a wide range ofdi/dtat zero current and peak forward thyristor currentIF, just before its current reversal. In the parameter extraction, the storage time and the ratio of fall time to storage time were assumed to be functions ofdi/dtandIF. For various thyristors, the extracted parameters fit both sets of the above-mentioned curves within an error of 8% over a 1:100 ratio ofdi/dtat zero current and over a 1:4 ratio ofIF.

DOI:10.1049/ip-b.1988.0012

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A digital technique is described for controlling the application and removal of base drive to parallel connected power transistors so that they switch on and off in synchronism, and with minimum power dissiptation. The control circuitry was designed specifically for integration on an uncommitted logic array to produce a dedicated integrated circuit. This circuit, together with its power transistor, associated base drive and emitter current sensing circuitry forms a power module which can be operated in parallel with other similar modules to form a switch mode power regulator of any required current rating.

DOI:10.1049/ip-b.1988.0013

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A general procedure for predicting the amplitudes of the magnetic induction components, resulting from multisinusoidal excitation of a non linear magnetic conductor, is presented. The magnetisation curve of the magnetic conductor is represented by a sine series. The amplitudes of the magnetic induction components are expressed in terms of the Bessel functions with arguments pro portional to the amplitudes of the exciting multi-sinusoidal input.

DOI:10.1049/ip-b.1988.0014

出版商:IEE    

年代:1988

数据来源: IET