The invention discloses a motor-driven hydraulic
system for a crane amplitude changing mechanism and an action method thereof, and belongs to the field of construction machinery. The motor-driven hydraulic
system comprises an electric driving device and a hydraulic device; a battery supplies power to a controller, the controller adjusts the rotation direction and rotating speed of an electromotor,the electromotor drives a
hydraulic motor, and when the
hydraulic motor reversely drags the electromotor, the electric driving device can achieve the reversing drag power generation
energy recovery;when the amplitude is increased, the electromotor rotates forward to drive the motor, pressure oil is output to be supplied to a rodless cavity of a
hydraulic cylinder, a
piston rod extends out, and the
electricity energy is converted into the
gravitational potential energy in the process; and when the amplitude in decreased, the electromotor rotates reversely, the pressure oil of the rodless cavity of the
hydraulic cylinder drives the electromotor through the
hydraulic motor, the electromotor is in a reversing drag power generation condition, the generated
electric energy is stored in the battery, and the energy can be reused when the amplitude is increased. According to the motor-driven hydraulic
system, the
gravitational potential energy of a jib and the sling load is recovered and utilized when the amplitude is decreased, the
energy consumption can be significantly lowered, the system efficiency is improved, and the heating is reduced.