In this thesis, surface vibration amplitudes and modes of piezoelectric transducers are studied. A system is developed to measure these amplitudes and observe the modes in different media. Piezoelectric transducers are used for underwater sound transmission. They are energized individually or in array form by continuous or pulsed electrical power and the acoustic energy is transmitted from the radiating front surface. This acoustic transmission and its beam pattern correspond to the vibration amplitudes and modes of transducer radiating surface when the electrical energy is applied. Optical techniques are the most common methods used to determine the small vibration amplitudes of objects and the Electronic Speckle Pattern Interferometry Technique (ESPI) has been used to detect the small movements of objects down to 10-20A in real time. Hogmoen and Lokberg have described a method for real time detection and have carried out measurements of small vibrations at frequencies up to 30 KHz . They claimed detection limits of 20A by visual observation and O.lA by photoelectric measurements using a lock in technique. In the thesis, the reference beam modulation is performed by an e1ectro-optic modulator in the path of the reference beam. This allowed ESPI to be used to measure high frequency vibration amplitudes into the MHz region semi-automatically. A video integrator gated by a digital scanner is used to sample the video information directly from a television screen. Various vibration modes of a PZT-4 transduter radiating surface were studied at its resonant frequencies in 3 different media. By using an automatic calibration procedure and a phase-sensitive detection technique, absolute vibration amplitude measurements were successfully carried out. Various experimental surface vibration modes are related to the theoretical values by using simple plate vibration theory which suggests that a PZT-4 transducer behaves like a simply-supported thin plate at low power levels. The relationship between transducer radiation beam patterns and the surface vibration amplitudes under water is presented in Chapter 8. An optical study of the Michelson Interferometer has been given alongside the speckle interferometer and the results of early experiments with the Miche1sori is presented. The reasons for abandoning the Miche1son Interferometer and using the speckle interferometer are given extensively in Chapter 1.

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A new model for piezoelectric ultrasonic transducers is proposed. Using a systems engineering approach, the concept of feedback is used to explain secondary piezoelectric effects and to clearly describe electro-mechanical interaction. The model is derived from the fundamental piezoelectric equations and it embraces the relevant practical situations where the transducer is subject to arbitrary electrical and mechanical loading. The following main features are incorporated within the model. a - It is valid over a wide range of frequencies, b - It is applicable in both transmission and reception modes, c - It involves realisable elements which are readily simulated, and d - piezoelectric, pressure and voltage interactions are clearly related. The model has been verified extensively in computer simulations and water tank measurements of transducer profiles. Extremely close substantiation of the theoretical analyses was obtained, and the model is considered to offer significant advantages over existing transducer analogies.

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This thesis is concerned with the development and testing of a dynamic simulation program for isolated, compact power systems of the type found in the marine and, off-shore environments. The modelling of electrical machines and their controllers is presented; the modelling of prime movers and governors is considered in detail and representations are proposed for the various driver; and loads encountered in these systems. The significant non-linearities in the systems are fully represented, A test procedure applied to an off-shore system is described and test results are presented. These are compared to simulated results for system and prime, mover responses to validate the simulation procedure adopted. In additions other validation procedures using data supplied by manufacturers are presented. These validation procedures are used to justify the mathematical representations of the, various subsystems and also to validate their co-ordination to form a complete system model. Results for a range of system studies are presented to indicate the range, flexibility and versatility of the overall simulation program.

In this thesis a thorough investigation of 4-reactor shunt compensated systems under unbalanced fault-transient conditions has been carried out. Mathematical models for incorporating 4-reactor compensators into single and multi-section feeder systems, together with the technique used to simulate reactor saturation, are developed. The techniques are very general, are applicable to transposed and untransposed multi-conductor lines of any configuration, and can take into account the frequency dependence of system parameters. Using these techniques computer programs are developed to study : a - Effect of shunt-compensation on primary system response. b - System and reactor overvoltages. c - The probability of reactor saturation and its effect on primary system wave forms and hence on the performance of distance protection. d - Effect of shunt-compensation on the performance of distance protection.

This dissertation is concerned with the improvement of the transient response of turbo-generator sets following a severe system disturbance. The improvement in response is obtained by the application of a single additional system state into the relevant controllers. The system state used is that of rotor acceleration. Theoretical studies are carried out to obtain the feedback gains required for single machine co-ordinate control of excitation and governing. The study is then extended to a multi-machine system. The control laws obtained from the theoretical studies are applied in the laboratory to micromachine systems. A method of obtaining a rotor acceleration feedback control signal is developed and applied to these laboratory micromachine systems. The acceleration transducer forms an essential part of a dedicated microprocessor data acquisition system, which, apart from the functions of data collection and processing, performs a real time simulation of the governor turbine model. The output of this simulation is then used to control the micro-machine prime mover torque. An essential feature of the microprocessor system is the determination of control laws for both the governing and excitations systems during transient conditions.

The synchronous reactances of a salient-pole synchronous machine are functions of the load of the machine because of the non-linearity caused by magnetic saturation. In the d-axis the machine is more saturated than in the q-axis, and for exact analysis appropriate saturated reactances have to be used. A three dimensional numerical solution of the field problem, based on network method is developed to calculate the reactance. The non-linearity of the magnetic materials, the complicated contours of the cross section of the machine, and the currents in the various windings are fully considered. The analysis is applied to the predetermination of flux and flux density in a homopolar linear synchronous machine. The flux densities are used to predict the magnetising inductances, by the use of a flux linkage method. The normal forces acting between the rotor and stator are also calculated in a number of different ways including the use of Maxwell's stress. The field is described and the simplifying assumptions arid boundary conditions are discussed. The governing equations for scalar potential in terms of network properties are developed from Maxwell's equations. The numerical solution of the linear set of network equations is obtained by successive over-relaxation and the nonlinearity is considered by an alternating relaxation procedure. The difficulties associated with the use of scalar potential have been overcome by considering the permeable region to be current free. All the current-carrying conductors are placed in the surrounding air. Equations for a simple air-gap calculation of the inductances and normal forces in a homopolar linear synchronous machine are derived. The leakage inductances produced by air-gap flux which fails to reach the rotor have been considered as parts of the magnetising inductances. Inclusion of these leakage components enables close agreement to be obtained with the measured voltages. The leakage components have no influence on the forces produced by the homopolar LSM. The good agreement achieved in a comparison between the calculated and experimental results for the homopolar linear synchronous motor, confirms the validity and accuracy of the network field calculation method. The mechanical and electrical characteristics of the homopolar LSM are compared with those already found for a heteropolar machine. The advantages and disadvantages of both these machines for advanced transport system are discussed in details. Methods for improvement of power factor and for reducing pole losses are also mentioned.