Mathematical modelling of a vector controlled LIM drive

The linear induction motor is often still considered to be a special-purpose machine that is tailored to meet specific needs, but it is slowly finding more applications with its added advantages over rotary motors. This thesis is concerned with the development of a mathematical model which provides the transient and steady-state performance of a current-regulated inverter-fed linear induction motor system. The linear induction motor is posed as a one-dimensional electromagnetic field problem, to provide a better understanding of the so called 'endeffect' phenomena, which accounts mainly for the difference in performance between the linear induction motor and its rotary counterpart. An equivalent circuit is described that takes into account these end-effect transients for a single-sided linear induction motor. An accurate model for the inverter switching action is developed and the performance of the complete system under various operating conditions is studied, and compared with experimental results obtained from published literature. A closed-loop control system is implemented, using conventional field-oriented control and a newer and simpler method known as Natural Field Orientation is investigated, and compared with both the direct and indirect field orientation methods. In Natural Field Orientation, a decoupled control of torque and flux producing components of current is easily achieved by using the machines inherent properties, to establish a correct field-orientation, and this allows the induction motor to provide a performance that combines the control characteristics of the dc motor with the merits of the induction motor.