The
desire to improve fuel efficiencies and reduce emissions
from large commercial vehicles has led towards an increased
use of electrically-driven auxiliaries in these vehicles. Electrical
auxiliaries permit increased efficiencies and reduced emissions
because their operation is independent of the main engine.
Of
particular benefit is the use of an electrical compressor for
the vehicle air conditioning unit which can be powered either
from an external shore supply or from an optional Auxiliary
Power Unit, either of which prevent the emissions problems
created by the need for the driver to idle the main engine
overnight to maintain power to the air-conditioning. Central
to the increased use of electrical auxiliaries within the truck
is the provision of a high-output, high-efficiency generator
in place of the conventional alternator.
An SR Drive® generator
has been developed which is suitable for mounting on the engine
in place of the existing vehicle alternator. The generator
has an outside diameter of 165mm, a length of 200mm and will
deliver a power of 7.3kW at 340V with a system efficiency of
between 80-90% compared with a maximum of 65% for the conventional
alternator. The generator uses liquid cooling derived from
the main engine coolant circuit and incorporates a number of
advanced manufacturing techniques to achieve the required thermal
performance in such a compact package.
The product development has
focused on both system level and component design with an emphasis
on reliability and robustness. State-of-the-art
control algorithms permit the SR Drive® generator to operate
without the need for a position sensor, maximizing system reliability
in the challenging engine-bay environment.
US ‘Anti-idling’ restrictions
Impending restrictions within
the US address the energy wastage and emissions problems caused
by truck drivers idling their main engines overnight to power
auxiliary loads: predominantly the air conditioning compressor. Conventional belt-driven auxiliary
loads require the main engine to be run at speeds in excess of
1000rpm to provide the necessary power. However, electrically
driven auxiliary loads are not directly tied to the main engine
speed and can thus be powered from a dedicated Auxiliary Power
Unit (APU): a small diesel-engined generator offering much higher
efficiency and greatly reduced emissions compared with idling
the main engine. Typical fuel savings over a one year cycle
are estimated at around 1,500 gallons per truck.
Of
particular benefit is the use of an electrical compressor for
the vehicle air conditioning unit which can be powered either
from an external shore supply or from an optional Auxiliary
Power Unit, either of which prevent the emissions problems
created by the need for the driver to idle the main engine
overnight to maintain power to the air-conditioning. Central
to the increased use of electrical auxiliaries within the truck
is the provision of a high-output, high-efficiency generator
in place of the conventional alternator. 
An SR Drive® generator
has been developed which is suitable for mounting on the engine
in place of the existing vehicle alternator. The generator
has an outside diameter of 165mm, a length of 200mm and will
deliver a power of 7.3kW at 340V with a system efficiency of
between 80-90% compared with a maximum of 65% for the conventional
alternator. The generator uses liquid cooling derived from
the main engine coolant circuit and incorporates a number of
advanced manufacturing techniques to achieve the required thermal
performance in such a compact package.