The work presented in this thesis is concerned with some aspects of power electronics largely related to the analysis and design of inverter-fed induction machines. Chapter 1 introduces the problems associated with the operation and analysis of inverter-fed induction machines, and state-of-the-art developments as highlighted in some recent publications. Chapter 2 is concerned with the development of induction machine frequency- and time-domain models and their solution methods. Methods of calculating model parameters are described. Simple and extended versions of the coupled circuit concept are developed for cage-rotor induction machines, and skin-effect is incorporated in these time domain mode is. Chapter 3 provides experimental verification for induction machine parameters and models described in Chapter 2. It also provides comparisons of measured and predicted results of dynamic tests for sinusoidal, quasi-square and sinusoidal PWM wave supply conditions. The measured and predicted results are shown to correlate reasonably well. Some specialised aspects of induction machines operation with non-sinu-soidal supplies such as peak transistor currents are also considered. Chapter 4 presents some design studies for the improvements of induction machine efficiency. Two machines are proposed; an improved 2-pole machine and an alternative 4-pole machine running at twice inverter frequency. For the same rotational speed and equal airgap magnetic and current loadings, the 4-pole version appears to have some advantage. Chapter 5 illustrates development of the time-domain induction machine models for use with the circuit analysis program ASTAP. Theoretical results of induction machine performance using ASTAP are shown to be the same as those obtained using the numerical step-by-step method, and correlate very well with experimental results. A special use of ASTAP was to model, as an equivalent circuit, the complete power-transistor inverter-induction machine system. Some examples of the interaction of the machine and inverter under fault conditions are presented.
|Date of Award||1982|