Series Drivetrain With CVT Output

An electric drive system for propelling a machine, the electric drive system comprising:

• first and second electric drive motors linked directly to a sun gear and ring gear respectively of a planetary output stage for driving a series drive train, the output of the planetary output stage being directly linked to a carrier of the planetary output stage, the planetary output stage including a ring brake for selectively braking and releasing the ring gear;
• an electrical energy supply system for supplying electrical power to the first and second electric drive motors;
• and
• a controller programmed to operate the first and second electric drive motors and the ring brake in two regimes of operation to provide a desired machine speed, wherein in the first regime of operation, corresponding to a first range of machine speeds, the controller actuates the ring brake to brake the ring gear, and actuates only the first electric drive motor at a speed sufficient to yield the desired machine speed, and wherein in the second regime of operation, corresponding to a second range of machine speeds higher than the first range of machine speeds, the controller drives the first electric drive motor at a fixed speed, actuates the ring brake to release the ring gear, and drives the second electric drive motor at a speed sufficient to yield the desired machine speed.

A method for operating an electrically driven output stage to a series drive train to power a machine, the electrically driven output stage including a planetary gear set having a sun gear, ring gear, and carrier, a ring associated with the ring gear to maintain the ring gear in a locked position, a first electric drive motor rotationally linked to the sun gear, a second electric drive motor rotationally linked to the ring gear, and the carrier being rotationally linked to the series drive train, the method comprising:

• receiving an indication of a desired machine speed;
• operating the first electric drive motor, second electric drive motor, and ring brake to yield a machine speed matching the desired machine speed by:
• employing the ring brake to stop the ring gear and the second electric drive motor, and actuating the first electric drive motor at a speed sufficient to yield the desired machine speed when the desired machine speed is below a predetermined threshold speed;
• and
• employing the ring brake to release the ring gear, operating the first electric drive motor at a predetermined fixed speed, and actuating the second electric drive motor at a speed sufficient to yield the desired machine speed when the desired machine speed is at least as high as the predetermined threshold speed.