摘要:

The paper describes the design and testing of an overvoltage damping filter supplied to the National Railways of Zimbabwe. The mechanism of overvoltage generation is explained, along with the need to limit overvoltage amplitude. An explanation of the choice of filter to reduce overvoltage is given, and the techniques used to derive the filter-component values and rating are described. A frequency-domain technique was derived to rate the filter components and this is different in some aspects from conventional filter-rating calculation methods. A Section covering protection and operating aspects is included, since many of these factors are unique to railway feeders. The paper terminates with a comparison between calculated rated values and measured filter currents and concludes that the methods chosen for the design are accurate.

DOI:10.1049/ip-b.1989.0033

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper presents a new Class E lowdvD/dtrectifier, its analysis and experimental results. The rectifier circuit contains a capacitor connected in parallel with a rectifying diode. The capacitor sets the conduction angle of the diode current, and the output-filter capacitor independently sets the AC ripple on the DC output voltage. The diode-junction capacitance is included in the parallel capacitance and threrefore does not adversely affect circuit operation at high operating frequencies. The diode turns on and off at lowdvD/dt, yielding low switching losses and low switching noise. Moreover, the absolute value ofdiD/dtat turn-off is limited by an external circuit, significantly reducing the reverse-recovery effect. For these reasons, the rectifier is especially suitable for high-frequency operation. Basic parameters of the circuit are derived, using time-domain analysis. The experimental and theoretical results were in good agreement.

DOI:10.1049/ip-b.1989.0034

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A general form of analysis is described that is capable of modelling cage induction machines with inter-rings (conducting rings joining all the bars of the cage, positioned along the length of the rotor stack). The model is verified using a commercially-manufactured motor. It is shown that, as far as torque is concerned, inter-rings have an effect which is opposite to that introduced by skewing the rotor.

DOI:10.1049/ip-b.1989.0035

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Since the demagnetisation curves of permanent magnets with knee points are not single-valued, hysteresis effects below the knee points need to be considered. A field problem with an unknown and nonuniform permanent-magnet source distribution occurs. A hysteresis model for simulating permanent magnets with such knee points is presented in the paper. By using the model and a permanent-magnet source-iteration method, the field problem can be easily solved by the finite-element method. The field solutions for both a single magnet and a magnet assembly, each air-stabilised, are computed by the presented method, and are found to be in good agreement with test results.

DOI:10.1049/ip-b.1989.0036

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A rigorous analysis of the static Kramer drive under steady-state conditions is described in which stator variables are transformed on to a frame of reference which is stationary with respect to the rotor. For constant-speed operation the system equations are reduced to a set of linear differential equations with constant coefficients which are solved to predict drive waveforms, allowing for inverter DC-voltage waveform, DC-link-current ripple and the changing states of conduction of the rotor rectifier diodes. Eigenvalue and eigenvector techniques are applied to obtain analytical expressions which greatly reduce computation time. The harmonic content of the various current waveforms is examined, and the analysis used to examine certain features of drive performance such as stator-current pulsations at certain speeds. Results were verified experimentally and display very good agreement with measurement.

DOI:10.1049/ip-b.1989.0037

出版商:IEE    

年代:1989

数据来源: IET

摘要:

In the paper we present a new type of cycloconvertor that is based on the static induction transistor (SIT). We also present a new control method, which we develop by using a pulsewidth-modulation (PWM) technique. The control algorithm is extremely simple in this method, enabling microprocessor-based control. A prototype six-pulse cycloconvertor is controlled by a small-scale controller based on TMS9995. The results show that many problems that arise when using the conventional cycloconvertor can effectively be solved by our new control method.

DOI:10.1049/ip-b.1989.0038

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The task of finding an optimal induction-motor design is defined as a discrete multicriterial optimisation problem. An approach to solving this problem through two-level optimisation is described. A bicriterial problem is solved by the assumption that all optimisation variables are continuous. Criterial functions in the example are material and operating costs of the motor. The possibility of applying two methods (multipliers and constraints) is considered and both these methods are employed in the optimisation process. Corresponding scalar optimisation problems are solved by means of a quadratic approximation method. An analysis of obtained optimisation results is performed, with the major conclusions that two local compromise solution sets exist and that the global compromise set in the decision space is not continuous. The computational model (more sophisticated than in the majority of other works dealing with the optimisation of an induction-motor design) and the synthesis program are briefly described. The results of design calculations are analysed mainly for two optimal solutions determined for minimal operating and material costs, although intermediate results are also presented.

DOI:10.1049/ip-b.1989.0039

出版商:IEE    

年代:1989

数据来源: IET