motor/generator
units. The intention
of the system is that the transmission ratio between the engine
and the final drive becomes continuously variable, allowing
the engine to be operated close to its peak efficiency at a
constant speed around 2000rpm.
Vehicle speed is then
controlled by the two SR Drive® ‘variator’ machines
whose maximum power output is a fraction (around a third) of
that of the diesel engine. The overall vehicle efficiency
is increased significantly by providing an infinitely variable
transmission with a combination of gears and small electrical
machines and yields an anticipated 10% improvement in vehicle
fuel economy.
The SR Drive® machines
use liquid cooling and have a continuous rating of 25kW from
1800rev/min to 11000rev/min. Each machine
has an active diameter of 192mm and an active length of 160mm. A
maximum torque of 135Nm is available for short periods of time. Position
sensorless control is used to provide a compact package suitable
for use in the engine bay. Continuous current control enables
a wide constant power region to be achieved from a DC bus voltage
of 425V using 100A IGBT’s* with a 70°C coolant temperature.
*IGBT – ‘Insulated Gate Bi-polar Transistor’ a
high efficiency semiconductor switching device.
Dual Mode Electric Infinitely Variable Transmission by Arnaud Villeneuve, Renault FRANCE
Aachener Kolloquium Fahrzeug und Motortechnik 2004
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