Hamm has launched a tandem roller with hybrid power train. The HD+ 90i PH combines a conventional internal combustion engine with a hydraulic accumulator. The diesel engine covers the base load while the hydraulic accumulator meets peak loads.
The underlying concept is based on the realisation that although the maximum load is called for regularly while compacting, it is always just for a few seconds at a time. This typically occurs when starting up or activating the vibration or oscillation for example. All other compaction tasks call for significantly less power. This is the reason Hamm has equipped the power hybrid roller with a smaller diesel engine in combination with a hydraulic accumulator to satisfy the load peaks.
The hydraulic system works like a pumped storage power station: as soon as the power demand falls below the maximum load of the internal combustion engine, a pump fills the hydraulic accumulator. If a lot of power is called for, the hydraulic system functions as an auxiliary drive, able to supply a maximum short-term load of up to 20 kW. Following this the cycle begins afresh with the refilling of the accumulator. The principle functions splendidly because the maximum power is usually only called up for a matter of seconds. Afterwards there is sufficient time to replenish the accumulator.
This technology allows the roller to deliver the same power while equipped with a smaller diesel engine. Two other components of the HD+ 90i PH also help to ease the load on the diesel engine: an efficiency-optimised electric fan drive and an efficient start-stop system. This means that for the HD+ 90i PH a 55.4 kW output engine suffices – instead of the 85 kW unit in the conventional version.
