More about the powertrain

More about the powertrain

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The petrol internal combustion engine itself is an innovation and was developed by CMC Power Systems. Of 1.4 litre displacement, the all-aluminium engine (called a ‘Scotch Yoke’) is a horizontally-opposed 4-cylinder design which is exceptionally compact and light (75 kgs). The compactness comes not only from the layout but also having the crankshaft moving within a slot in the centre of the con-rod. This arrangement makes for improved combustion efficiency and efficient low-vibration operation. The engine is also suited for stop-start running that would be typical for a HEV. Maximum power from the engine is 60 kW(81.6 kW) at 5500 rpm. The engine is only used for generating electrical power which is stored in lead-acid double-impact gel-type batteries. The battery pack provides enough energy for the electric motor to run for 20 minutes continuously, but under normal operation, the batteries would be periodically recharged as the car is in motion.

One of the advancements in hybrid powertrain technology that is found in aXcessaustralia LEV is the use of Supercapacitors. Commonplace in telecommunications devices, supercapacitors have never been used in high-power applications until now. Those in the car were developed by CSIRO and use a carbon coating in an organic electrolyte to form what is termed a “double-layer capacitor”. This new technology is claimed to deliver some of the highest capacity-to-power ratios reported anywhere in the world and gives the aXcessaustralia LEV an unique advantage compared to other HEVs.

The energy storage system is unique and part of the Surge Power Unit (SPU) which includes the Supercapacitors. The SPU absorbs rapid bursts of energy created during braking and then provides the surge of power needed for acceleration. This means that even though the engine is small, it is more than enough for acceptable performance and also to run efficiently.

The energy is used to power the water-cooled 300V Electric Traction Motor (ETM) which uses a new switched reluctance motor technology that was specifically developed for traction applications. Torque is impressive – 300 Nm – while the available power is 110 kW (150 bhp), which would give the aXcessaustralia LEV respectable performance. With electronic systems, it can be programmed to have various characteristics and in the aXcessaustralia application, it is programmed to give a wide constant power characteristic, thus eliminating the need for a mechanical gearbox. In fact, there is no gearbox at all and the motor simply runs fast or slow, according to the pressure on the accelerator pedal.

It would be evident that power controllers take up a huge amount of space in the car. This is, however, due to the fact that the unit is the only one built and miniaturisation would be far too costly for the purpose. Nevertheless, if mass produced, the power controllers could be as small as a normal briefcase.

The water pump is also unique and extremely practical in design because it is not driven by a fan belt or the engine; it draws no horsepower and is draws operating power from the battery pack.

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