Dynamic Performances of AC Drives Fed from Power Transistor-Thyristor Inverters

A simulation procedure has been pointed out for investigating problems concerning road traction drives based on three-phase induction machines supplied by modulated inverters. The inverter employed is not conventional because it utilizes both thyristors and power transistors. The solution proposed allows weight and size to be minimized with respect to a conventional thyristor drive. As a consequence, the design presented meets, in a satisfactory way, the requirements of a drive that is to be used in an electric vehicle, In the simulation, the inverter is represented as an independent voltage generator which produces various voltage waveforms at the ac terminals. The induction machine is described according to a dynamic model based on Park´s two-axis theory. A computer program has been used for simulation of the drive dynamics, and some quantitative results have been obtained with reference to an actual traction drive.