Patent ID: 8505290

Claim:
A drive for rotating a rotating structure ( 20 ) rotatably mounted on a non-rotating structure ( 11 ), the drive comprising: an electric motor ( 32 ) which receives electricity and generates driving force; a hydraulic mechanism ( 40 , 110 ) which receives hydraulic fluid and generates driving force; and an output shaft ( 35 ) which is driven to rotate by the electric motor ( 32 ) and the hydraulic mechanism ( 40 , 110 ), wherein an operation of driving the output shaft ( 35 ) only by the hydraulic mechanism ( 40 , 110 ) is selectively performed when rotation speed of the rotating structure ( 20 ) is lower than a predetermined reference speed, and an operation of driving the output shaft ( 35 ) only by the electric motor ( 32 ) is performed when the rotation speed of the rotating structure ( 20 ) is not lower than the reference speed.