A softstarter for starting and stopping an asynchronous motor having three phases, including two pairs of semiconductor devices of the type turning off at zero-crossing of the current therethrough, wherein each of the two pairs of semiconductor devices is connected in anti-parallel, and the first pair of the semiconductor devices is adapted to control the voltage of one of the phases of the motor and the second pair of the semiconductor devices being adapted to control the voltage of another of the phases of the motor, a DC reducing unit associated with the two pairs of semiconductor devices, a first voltage measuring unit for measuring voltages across the two pairs of semiconductor devices, and a first zero-crossing detecting unit configured for detecting zero-crossings of the measured voltages across the two pairs of semiconductor devices and providing zero-crossing signals to the DC reducing unit.