Induction motors are widely used in industrial applications because of their cost-effectiveness and high reliability. However, when a momentary power interruption occurs, the motor enters a free-running state driven by inertia. Under this condition, improper restarting may cause significant inrush currents, torque shock, and mechanical stress. This paper proposes a fast and stable sensorless restart strategy for induction motors. The proposed method applies three short-circuit current pulses during the free-running state to estimate the time-varying rotor speed and acceleration. Based on the estimated speed and acceleration, a short-circuit voltage–current model of the induction motor is employed to calculate the rotor flux axis position. The proposed strategy requires no additional power consumption, allowing rapid and reliable restart operation. As a result, the restart time is significantly reduced compared to conventional approaches, while stable and robust performance is maintained over a wide rotor speed. The effectiveness of the proposed strategy is verified through simulation results under nonlinear load conditions.
