2003-01-0712 Mechatronic Solution for Electronic Turbocharger

An innovative way of lowering engine fuel consumption is to reduce engine displacement. However, smaller engines featuring reduced swept volume typically exhibit insufficient torque at low engine speeds. Conventional exhaust turbochargers are not able to compensate for this behavior and additionally suffer from the familiar turbo lag. One possible solution may be an electrically assisted turbocharger, with a high-speed motor providing the extra boost at low engine speeds.
A critical factor for the efficiency of the concept is the ratio of the electric motor torque and the rotational mass inertia of the rotor. Testbench evaluation shows acceleration times of 0.5 seconds to reach speeds up to 70,000 rpm. Typically, the electrical load of such systems goes up to 3 kW. Target motors are various types of electrically commutated motors such as BLDC, switched reluctance or induction motors.
This paper describes a system solution for controlling high-dynamic motors like the one used for the electrically assisted exhaust turbocharger (e-turbo). It presents the strengths and the limits of the solution.