Electric supercharger operates continuously at high boost levels

31st July 2015
Nat Bowers

Aeristech has announced what it claims to be the first electric supercharger capable of continuous operation at high boost levels. Independently validated by Ricardo and MAHLE Powertrain UK, the technology provides greater efficiency and easier packaging than a mechanical supercharger or a two-stage turbocharger.

Aeristech has overcome the thermal management issues that can restrict other electric boosting devices currently available on the market to only transient operation by using permanent magnet motor technology in place of the more usual switched reluctance type. This has been made cost-effective by developing a patented control and switching technology that enables the use of many cost-competitive components.

Bryn Richards, CEO, Aeristech, commented: “Our system can deliver over 2.5bar of boost pressure continuously, setting it apart from other systems which only offer short duration boost assist for improving the engine transient response. By using a 48V architecture, we have provided a solution that is easily implemented and competitive in cost for the growing numbers of hybrid and mild-hybrid vehicles that will be launched in the next few years.”

Aeristech’s 48V eSupercharger has already been demonstrated by MAHLE Powertrain UK in a D-segment appraisal vehicle using its downsized 1.2 litre, 3-cylinder gasoline engine. The engine achieved 33bar BMEP at 2000rpm – an astonishing 313Nm for an engine of this capacity - and a maximum power output of 193kW.

“By replacing the smaller turbo in a two-stage turbocharging arrangement with our eSupercharger, MAHLE Powertrain UK was able to increase the size of the main turbo without concerns over driveability and transient response,” added Bryn. “The eSupercharger can not only help increase specific output but is also much easier to accommodate within the engine compartment than a second stage turbocharger because it has greater layout flexibility.”

Using an eSupercharger also has advantages for emissions control. Because it is applied to the inlet side of the engine, it reduces the thermal mass in the exhaust stream which helps to maintain catalyst temperature, especially at lower speeds and loads.

Aeristech’s motor control strategy separates commutation and power control which means the electrical switching frequency need be no higher than running speed. This fundamentally new approach dramatically reduces the cost of many key switching components while ensuring exceptionally accurate high-transient speed control.

The company’s expertise in permanent magnet e-machine design means the motor has class-leading power density and low inertia. The eSupercharger operates at up to 150,000rpm with a transient response of idle-to-target speed in under 0.4 seconds.

“We are the first company to make high performance permanent magnet motors sufficiently cost-effective for eSupercharger application. It means we completely avoid the thermal issues that arise with switched reluctance motors, enabling us to provide continuous high boost levels. Together with the imminent arrival of 48V architectures throughout the industry, this will enable more downsizing and higher engine efficiencies, leading in turn to vehicles with lower CO2 emissions and better driveability,” concluded Bryn.

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