Development and analysis of novel soft-starter/energy-saver topology for delta-connected induction motors

A thyristorised star/delta switch is proposed as a soft starter and energy saver for delta-connected induction motor drives. A low-cost microprocessor-based hardware is developed and used for the control of the star/delta switch. The use of the star/delta switch for starting is first explained followed by its application as an energy saver. Three schemes of switching transitions are proposed and implemented for the star (delta) to delta (star) changeover process. Extensive simulation and experimental results are presented to show that the proposed circuit is a promising candidate as a starter/energy saver for delta-connected induction motor drives.