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Electric Power Applications, IEE Proceedings B

Issue 4 • Date Jul 1993

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Displaying Results 1 - 6 of 6
  • Maximising the saliency ratio of the synchronous reluctance motor

    Page(s): 249 - 259
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (940 KB)  

    Recent interest in the synchronous reluctance motor has increased in the context of possible applications in field oriented AC drives. The absence of rotor slip losses and the apparent simplicity of the control suggest the possibility of performance and cost advantages over the induction motor. With field oriented control, and continuous shaft position feedback, the synchronous reluctance motor does not need a starting cage and can be designed for maximum saliency ratio (L d/Lq ratio). This ratio is by far the most important parameter for achieving high power factor, torque/ampere, and constant-power speed range. This paper analyses the various known forms of the synchronous reluctance motor, to determine the maximum achievable saliency ratio and identify the parameters on which it depends. The main originality is the analysis of the effect of the number of flux guides/barriers. It is shown that a minimum number is required for the performance to surpass that of the induction motor. The analysis also reveals the optimum ratio of flux guide/flux barrier thicknesses and the effects of the tooth/slot geometry and stator saturation. Test results are included from three motors ranging from 50 W at 2000 r.p.m. to 7.5 kW at 1500 r.p.m., covering both axially laminated and transversely laminated types View full abstract»

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  • Design optimisation of a superconducting AC generator

    Page(s): 267 - 272
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    The feasibility of applying rational methods of optimisation to a superconducting generator design is presented. A new design method is developed which permits the optimisation of a superconducting generator to take place. The method is used in a computer program software package which systematically determines the optimum design parameters of the machine components. The optimisation techniques and the logical structure of the computer package are described. The optimisation problem is solved by using the interior penalty function method in which the direct search methods of Hook-Jeeves (pattern) and Nelder-Mead are used. A numerical example demonstrating the effectiveness of the program is given. A new analytical method is also presented for the prediction of the inner rotor bursting speed by taking into account the geometry, the applied stresses and material properties. The result of this method is used as mechanical performance constraints. Moreover, analytical presentation of other machine performances such as the critical characteristic of the superconductor are presented View full abstract»

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  • Design of currents to reduce torque ripple in brushless permanent magnet motors

    Page(s): 260 - 266
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    A method to design an improved motor excitation for three-phase brushless permanent magnet motors is presented. The unique motor excitation reduces ripple in the developed torque, reduces the effects of cogging or detent torque, and is also a minimum average power excitation. Practical benefits are reduced vibration and acoustic noise in speed control applications, and improved accuracy in position control applications. First, an analysis of torque ripple is presented using the exponential Fourier series in the torque model. The analysis is simple, yet extends some well known results by predicting the presence of additional harmonic components. Next, the design of an optimal weighting of stator current harmonics is cast as a type of constrained minimisation problem. In contrast to iterative approaches that have been reported in the past, the new design method determines the current harmonic weights in closed form. Steps in the design procedure are demonstrated using measured back EMF data from a 2 hp brushless DC motor View full abstract»

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  • Fast AC train emergency rescheduling using an event driven approach

    Page(s): 281 - 288
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    The authors report the development and implementation of an algorithm for the online timetable checking and rescheduling of the 50 Hz single-phase overhead current collection catenary system currently in operation in Hong Kong. Running as an online consultant on a personal computer, this algorithm allows operating personnel to perform checking of a proposed time table under various feeding conditions, to see whether runtime and traffic requirements can be met without causing any overloading. By using the event-driven approach, the computing time for checking each timetable is extremely fast. Owing to simplicity of this approach, various rescheduling schemes may be devised to suit different requirements of operational sophistication View full abstract»

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  • Dimensional analysis of the linear induction motor

    Page(s): 273 - 280
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    A steady-state mathematical model for a general linear induction motor (LIM) is evaluated from a transient model based on complex phasor analyses. All basic parameters of a LIM such as pole pitch, airgap width, slot width, slot depth, winding pattern, etc. are incorporated into the model by means of efficient factors, most of them dimensionless. The influence of these parameters and/or factors on specific LIM properties is analysed. Saturation and skin effect, as well as allowable (stator) current densities, defines the workable limits of both model and LIM. The model needs to approach reality reasonably well and must also be simple so as not to loose insight into its essential possibilities. Therefore, use has been made of hyperbolic airgap factors to replace the Maxwell field relations which actually determine the problem. The validity of the model in question is demonstrated by force measurements on some types (single-sided, tubular, slotless) of laboratory built LIMs View full abstract»

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  • Design and implementation of a high performance induction motor servo drive

    Page(s): 241 - 248
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    The design and implementation of a high performance induction motor servo drive system is presented. An experimental indirect field-orientated induction motor drive system is implemented, and its dynamic model is built up using stochastic techniques. To obtain good dynamic responses both in the position command tracking and load regulation characteristics, a position servo controller with two degrees of freedom is proposed. The parameters of the controller are found using a systematic design procedure according to the given drive specifications. The theoretic basis of the design procedure is developed in some detail. Having tested the performance of the controller by simulation, the microcomputer-based realisation of the designed controller has been successfully implemented. Some experimental results are given to demonstrate the effectiveness of the proposed position servo controller View full abstract»

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