Sensorless Soft Starter Torque and Flux Control Algorithm for Induction Motors

This article presents the soft starter torque and flux control (STFC) control method for soft starters, which combines the advantages of firing angle-based and predictive methods. This method is suitable for both starting and braking processes and is being specifically developed into a sensorless approach to ensure smooth integration into industrial products. Measurements on typical applications indicate that the STFC method increases performance, minimizes motor and thyristor losses, and thus enables more starting and braking operations per hour with the same hardware. The implementation is simple and based solely on vector comparisons.