US Department of Energy has provided funding to Caterpillar
to investigate the benefits of increased electrical auxiliaries
for highway trucks. Electrical auxiliaries
include the oil pump, the water pump, the air compressor for
the vehicle brake system and an electric HVAC (Heating Ventilation & Air
The heart of the system is the SR Drive® starter/generator
unit which is mounted between the engine and gearbox inside a
modified flywheel housing. The intention of the starter/generator
is both to provide a direct-drive capacity to start the engine
and also to generate the required electrical power for the various
Nidec SR Drives Ltd supplied
a 340V, 1200Nm, 30kW crankshaft mounted SR Drive® starter-generator
designed specifically to fit within the challenging space envelope
occupied by the conventional flywheel and clutch.
The system uses position sensorless control to provide rapid
engine starting and to maximise system reliability in the extreme
environment in which it is located.
Extensive on-highway trials
have shown the system to be robust, requiring no maintenance
intervention since the truck was commissioned in 2003. The
same trials have confirmed a significant fuel economy benefit and work is
underway to make further improvements by increasing the functionality
of the ISG to provide engine assist during pull away.
Developed as part of the US DoE programme reference DE-FC04-2000AL67017.