The HD+ 90i PH double drum compactor has a hybrid power train system that combines a conventional diesel engine with a hydraulic accumulator. It uses the engine to handle base loads on the machine and the hydraulic accumulator to assist in meeting peak loads.
Hamm engineers studied engine loading during compaction and determined that peak loads occur infrequently and are of short duration—for example, when the roller first begins operation or the vibration/oscillation system is activated. In the new hybrid-power roller, these brief peak loads are handled by hydraulic assist, which allows using a smaller engine (74 horsepower versus 114 horsepower) with no compromise in performance, says Hamm. The load on the diesel engine is reduced further by electrically operated cooling fans.
The hydraulic-assist system, explains Hamm, works in a manner similar to a pumped-storage power station: when power demand falls below the maximum load of the engine, a pump fills the hydraulic accumulator. When peak power is required, such as starting the vibration drive, the hydraulic system functions as an auxiliary drive and supplies a short-term boost of up to 27 horsepower. Further advantages of the system, says Hamm, include the smaller engine not requiring an SCR converter or DEF fluid, as well as the smaller engine’s quieter operation. The hybrid power train, in combination with electric fan drives and a start-stop system, says Hamm, yields fuel savings of up to 15 percent.
The hybrid system was tested in field trials in select markets during 2016 and 2017 and is expected to be available in North America for models with double-vibration, vibration-oscillation, and smooth-drum-pneumatic configurations in 2018.