### Browsing by Subject "Electronic and Electrotechnical Engineering"

Now showing 1 - 5 of 5

###### Results Per Page

###### Sort Options

- ItemOpen AccessDirect digital control of a synchronous machine(1977) Tatlow, Gavin Mark; McLaren, S GWith the advancement of thyristor technology, variable speed alternating current drives are providing improved performance over conventional systems. The aim of this thesis is to investigate the possibilities of direct digital control of a thyristor converter and to determine the major parameters affecting the operation of a variable speed synchronous machine drive.
- ItemOpen AccessInduction motor drive for battery vehicle(1978) Malengret, Michel; Enslin, NC de VA 9 phase transistor inverter fed induction motor for a battery vehicle with direct wheel drive is discussed. A new method of motor voltage control by pulse, width modulation, where the phases are interlaced in a manner to conserve continuity of the supply current, is described. In addition to this, a novel construction, where the motor and the inverter are built into one compact and economical unit, is presented.
- ItemOpen AccessInduction motors with modulated terminal voltage(1978) Schauder, Colin David; Enslin, NC de VFollowing the development of high speed solid state switches for the forced commutation of current in AC power circuits it has become feasible to apply forced commutation techniques to the frequency and voltage control of induction motors as variable speed drives. The availability of these methods raises questions regarding their effect on the performance of the motor and the generation of harmonic currents in the electrical supply. After the initial use of numerical simulation in the study of these systems it became apparent that this approach was not suitable for the evaluation of steady state performance factors. This thesis sets out to establish an analysis of the induction motor under these conditions which leads to the algebraic formulation of the performance of the system in the steady state. This approach can be used in any situation where the electrical supply to an induction motor is modulated by switching techniques. The analysis has been applied to chopper modulation of the supply voltage and also to a phase-stepping frequency convertor which incorporates chopper modulation. Experimental results are included to illustrate the validity of the analytical method.
- ItemOpen AccessOn the synthesis of optimum monopulse antenna array distributions(1986) McNamara, Derek Albert; Denbigh, P NThe stringent specifications of modern tracking systems demand antennas of high performance. For this reason arrays are finding increasing application as monopulse antennas. A new exact procedure is introduced for the synthesis of optimum difference distributions for linear arrays of discrete elements, with a maximum sidelobe level specification. The method is based on the Zolotarev polynomial, and is precisely the difference mode equivalent of the Dolph-Chebyshev synthesis for sum patterns. When the interelement spacings are a half-wavelength or larger the element excitations are obtained in a very direct manner from the Chebyshev series expansion of the Zolotarev polynomial. For smaller spacings, a set of recursive equations is derived for finding the array excitation set. Efficient means of performing all the computations associated with the above procedure are given in full. In addition, a set of design tables is presented for a range of Zolotarev arrays of practical utility. A novel technique, directly applicable to arrays of discrete elements, for the synthesis of high directivity difference patterns with arbitrary si delobe envelope tapers is presented. This is done by using the.Zolotarev space factor zeros and correctly relocating these in a well-defined manner to effect the taper. A solution to the direct synthesis of discrete array sum patterns with arbitrary sidelobe envelope tapers is introduced. In this case the synthesis is also done by correct placement of the space factor zeros. The above techniques enable high excitation efficiency, low sidelobe, sum and difference pat terns to be synthesized independently. Contributions to the simultaneous synthesis of sum and difference patterns, subject to specified array feed network complexity constraints, are also given. These utilise information on the excitations and space factor zeros of the independently optimal solutions, along with constrained numerical optimisation. The thesis is based on original research done by the author, except where explicit reference is made to the work of others.
- ItemOpen AccessReal-time distributed system architecture using local area networks(1992) Young, Richard; Ventura, M J EThis dissertation addresses system architecture concepts for the implementation of real-time distributed systems. In particular, it addresses the requirements of a specific mission and real-time critical distributed system application as this exemplifies most of the issues of concern. Of specific significance is the integration of real-time distributed data services into a platform-wide Information Management Infrastructure. The dissertation commences with an overview of the system-level allocated requirements. Derived requirements for an Information Management Infrastructure (IMI) are then determined. A generic system architecture is then presented in terms of the allocated and derived requirements. A specific topology, based on this architecture, as well as available technology, is described. The scalability of the architecture to -different platforms, including non-surface platforms, is discussed. As financial considerations are an important design driver and constraint, some anticipated order-of-magnitude system acquisition costs for a range of system complexities and configurations are briefly reviewed. Finally some conclusions and recommendations within the context of the allocated and derived requirements, as well as the RSA's politico-economic environment, are offered.