A generator includes: a built-in voltage controller disposed inside the housing of the motor and connected to the stator; a loop changeover switch, wherein one side of the three groups of loop polar phase contact points is connected to the current output unit through three phase lines, and the other side is connected to the current output unit through three loop lines; a three-phase short-circuit changeover switch is in a spaced arrangement with the loop changeover switch and includes three groups of short-circuit polar phase contact points, one side of which is connected to each other through short-circuit wire, and the other side is connected to each phase line; three converted-voltage output lines, wherein one end electrically connected to the loop polar phase contact points of the loop changeover switch is connected to one side of the loop lines; the other end is used to connect to a power device.