Included herein is a circuit comprising resistors, capacitors, relays, diode bridges, TRIACs, and DIACs mounted to a substrate. The circuit may be electrically connected to a user device containing a wide range of types and specifications of AC induction motors. The circuit may be installed “plug-and-play” onto a user device, without the need for tools, custom installation or deconstruction of a user device. Upon user direction or automatically, the circuit may inject DC current into the user tool which generates a stationary magnetic field inside the AC induction motor causing deceleration/arrestment of the AC induction motor's rotor. The circuit may prevent unintended acceleration of the rotor upon powering on the user device. Also included is a method for prevention of unintended acceleration of the rotor upon powering on the user device. Also included is a method for decelerating/arresting an AC induction motor.