Design of Fuzzy Logic based Soft Starter for Induction Motor

Induction motors are extensively used across all industrial applications due to the robustness, comparatively less cost and very low maintenance. Nevertheless, at startup, this kind of motors pull a largely high current about several times larger than the rated value harming both. Several starting methods have been employed to minimize the in-rush current and overcome this problem. Previously, conventional starting methods: direct-on-line (DOL), star-delta and autotransformer starters have been utilized since they generally provide minimal relative control of starting performance. This paper presents a soft starting technique for three-phase squirrel cage induction motor using fuzzy logic controller (FLC) based approach. The proposed solution uses a power electronic AC voltage regulator to slowly decrease stator voltage at start up, which reduces start current and torque fluctuations. A fuzzy logic controller uses from linguistic rules and membership function in determining the control action, based on the inputs (current error and its derivative). Simulation and analysis validate the proposed method. The results clarify a significant drop in inrush current and attaining a soft torque which improves the overall performance and service life of the motor. The proposed system offers a more stable start and effective operation of motor cores over conventional starting method