In a gear system containing planetary gears, because of the existence of the planetary carrier, there can be three rotating shafts to allow power input/output, and if necessary, one shaft can be limited to rotate by means of clutches or brakes, and the other two shafts are driven, so that there can be a combination of various gears engaged with each other:
Power is input from one sun gear and output from another sun gear, and the planet carrier is braked by the braking mechanism;
Power is input from a sun gear, output from the planetary carrier, and the other sun gear brakes to death;
Power is input from the planetary carrier, output from one sun gear, and the other sun gear brakes to death;
Two powers are respectively input from two sun gear, and then synthesized and output from the planet carrier;
Two paths of power are respectively input from the planetary carrier and one of the sun gear, and output from the other sun gear after synthesis;
Power is input from one sun gear, and output from another sun gear and planetary carrier in two ways;
Power is input from the planet carrier and output from two sun gear in two ways.