Steady State Analysis of Thyristor Controlled Three Phase Induction Motors Using State Space Techniques

The steady-state analysis of a three phase induction motor with a pair of back to back connected thyristors in each line is presented. A mathematical model suitable for the analysis is developed. The model retains the stator currents unaltered, whether the neutral is connected or not. This facilitates the application of current constraints introduced by thyristors and of boundary matching conditions needed for the steady-state analysis. State space modelling is employed and the initial condition vector pertaining to steady-state is obtained directly. The need for digital simulation of the characteristics of thyristors and integration from arbitrary initial conditions are avoided. The method is well suited for digital solution, easy to programme and fast in execution.