Magnetic attraction

An electrical generator and control system that could improve the fuel efficiency and performance of hybrid cars has been developed by UK engineers.

Electrical power-generation specialist Newage International developed the small, lightweight generator, based on a permanent magnet, with Durham University researchers. The company has established a small production facility in Stamford, Lincolnshire, capable of manufacturing up to 10,000 generators a year.

The Egshev (Engine/Generator Sets for Hybrid Electric Vehicles) is an axial flux, permanent magnet, toroidal generator. Axial flux generators are shorter and more compact than conventional radial flux generators, making them easier to integrate within the gearbox and transmission of hybrid cars.

This is because the rotor and stator in an axial generator are both disc shaped, and the magnetic field passes between the two discs in a direction parallel to the machine’s axis. In contrast, radial flux generators consist of a cylindrical rotor and stator with a cylindrical air gap in between, a configuration that wastes space.

Axial flux generators have an efficiency in excess of 90 per cent across a wide speed range, and fewer components, and can be used to start the engine, replacing the heavy starter motor. The device can also be bolted directly to the engine crankshaft, replacing theflywheel, said Dr Nazar Al-Khayat, chief engineer at Newage.

This eliminates the need for special couplings, and means the generator has no bearings, which can wear out. ‘We have created a very close coupling to the engine, which helps to reduce the overall size and packaging,’ he said.

Reducing the number of moving parts should increase reliability and durability, while the device is cheaper to produce than conventional generators. Using a permanent magnet reduces the generator’s weight, increases its efficiency and makes it easier to control, he said. ‘We are taking these advantages and putting them in an axial rather than radial-type machine.’

To ensure optimum efficiency, the engineers developed anelectronic control system to regulate output. ‘We are controlling the output by electronics, taking a variable voltage and converting it into a fixed voltage,’ said Al-Khayat.

The team tested the device using Ford and Nissan engines, at various speeds and under differing conditions, and the firm is now talking to car makers about producing the system for hybrid vehicles.