The device (10) has a synchronous motor (12) connected with an inverter (16), and a mechanical energy buffer (14) that is energized from an energy supply network (20). The energy buffer includes an asynchronous machine (24) for converting the mechanical energy into electrical current. A switch device (18) for electrical connection of the synchronous motor with the asynchronous machine is controllable by a control device (34), during a quasi-stationary operating condition. The asynchronous machine is electrically directly connectable with the synchronous motor by the switch device. An independent claim is also included for a method for operating a drive device.
