The invention discloses a novel
motor speed reduction protection device, which includes a
voltage detecting circuit, a logical judging circuit, a
driving circuit, and a power circuit. When a motor pulls heavy objects beyond pulling capacity of the motor or a certain unexpected situations, the motor loses driving capacity, the heavy objects fall rapidly,
speed reduction of the motor happens, and
counter electromotive force generated by the fast revolving motor can rapidly elevate the
bus voltage of a controller; the
voltage detecting circuit detects the
bus voltage, and then transmits the
bus voltage to the logical judging circuit to conduct calculation and judgement; when protection actions need to be adopted, signals are transmitted to the
driving circuit, the
driving circuit prompts a switch K to act, and the connection between the motor and the controller is
cut off; and meanwhile the motor and a discharging circuit are connected, braking force is generated by the motor, acceleratedspeeds of the falling heavy objects are lowered greatly, and damage is further reduced.