a series - wound motor , wherein , for braking purposes , the polarity of the armature of the motor is reversed for the opposite direction of rotation . the current supply for the motor is maintained until the armature comes substantially to a standstill and subsequently , the current supply to the motor is interrupted . the braking time is controlled in dependence upon operating parameters . for example , the braking time can be controlled by a predetermined time constant for the interruption of the current supply . to prevent running in the opposite direction , a reversal preventing device can be provided .