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English   Mercedes Citaro G BlueTec Hybrid
07.08.2009 von admin

Four electric wheel hub motors drive two axles

The actual drive power to the wheels of the Citaro Hybrid is provided by four electric wheel hub motors on the centre and rear axles of the bus. These motors develop a maximum output of 80 kW each and are liquid-cooled. The total wheel hub motor output of 320 kW is ample for an articulated bus, even under strenuous operating conditions. Two-axle drive, meanwhile, provides better traction. Also, the fact that in principle it would be possible to control the four wheel hub motors individually opens up interesting possibilities in terms of traction control and the use of electronic safety systems.

A 650-volt high-voltage intermediate circuit handles the power transmission between the generator, battery and wheel hub motors. The fact that the diesel engine is mechanically decoupled from the drive train and that energy can be recuperated from braking allows new control strategies to be implemented in order to reduce emissions. For example, the braking energy recuperated when pulling into a bus stop or coming to a stop at traffic lights can be used to provide electrical power when the vehicle is stationary or when moving off.

CleanDrive Technologies: Citaro G BlueTec Hybrid

Emission-free stopping, standing and starting at the bus stop

When drawing into, standing at and accelerating away from bus stops, the hybrid bus can operate in electric-only mode, which is virtually emission-free. A further plus point is that the vehicle can hardly be heard stopping and starting at bus stops or traffic lights.

A big advantage of the serial hybrid drive in the Citaro is down­sizing: instead of the large 12-litre six-in-line OM 457 hLA engine normally used in the articulated model, the hybrid bus is fitted with a compact OM 924 LA unit which develops maximum power of 160 kW (218 hp) from a displacement of 4.8 litres. This reduces the weight of the engine from approximately 1000 kg to around just 450 kg.

Since the diesel engine of the Citaro G BlueTec Hybrid does not drive the vehicle directly, it is not required to produce peak outputs and is therefore able to operate very econo­mically and with low environmental impact over a narrow rpm range at or close to its peak efficiency. The torque curve of the hybrid-bus engine is there­fore tailored predominantly to steady-state operation, for optimal emissions performance and fuel efficiency.

CleanDrive Technologies: Citaro G BlueTec Hybrid

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