Jaguar Land Rover (JLR) has developed an experimental Electric Drive Module (EDM), which it says is capable of producing up to twice the power and torque of those currently found in high volume production applications.
Designed to fit between the engine and transmission, the modular EDM system covers a range of different applications. At its core is a radial flux motor packaged inside a short, cylindrical housing, along with a clutch pack and a slave cylinder.
In plug-in hybrid (PHEV) form it uses a copper-wound neodymium synchronous permanent magnet motor running up to 8,000rpm. This produces around 150kW and 400Nm of torque, while comparable production systems are generally in the region of 50 to 70kW and 120 to 200Nm.
JLR has tested the PHEV version of the system in a modified Range Rover Sport fitted with a prototype 2-litre four cylinder turbocharged gasoline engine producing around 300bhp. The engine is packaged longitudinally with an eight speed automatic gearbox, while the EDM draws its energy from a 320-volt lithium ion battery back stored in the boot.
“We looked at every element of the design to optimise the power within a very small axial space,” said Mark McNally, JLR’s senior manager, Advanced Research Technology Demonstration. “We worked in collaboration with Motor Design Ltd on the electromagnetic performance. Newcastle University worked on the mechanical design and the packaging density, maximising the magnetic flux in the system. All this helped us to deliver such a high degree of performance in such a confined space.”
At the other end of the spectrum, the EDM in the mild-hybrid (MHEV) car uses ferrite magnets and aluminium windings to produce a cheap and exceptionally compact system. It produces 15kW and 50Nm – enough to act as a starter motor generator unit, as well as providing torque-filling and a low-speed creep functionality before the combustion engine kicks in.
Jaguar Land Rover has trialled this version in a development vehicle based on the Range Rover Evoque, where the EDM is fed by a 48-volt lithium ion battery pack and coupled to an experimental three-cylinder 90 PS diesel engine, driving through a nine speed automatic gearbox. Significantly, this engine is mounted transversely in the chassis, placing an even greater emphasis on packaging.
“It’s very slim in terms of axial length on the MHEV,” said McNally. “Plus, the mild-hybrid is a more transient system and the aluminium windings present benefits in terms of thermal inertia.”
By placing the EDM in between the engine and the transmission and using a clutch pack to control the drive, the system can decouple the combustion engine during regenerative braking to eliminate pumping losses. It also means a coasting function can be integrated.
The EDM work is part of a wider two year £16.3m research project, involving 12 technology partners and part-funded by the Innovate UK. At present it’s just a research programme, but JLR will be taking a close look at the findings, with a view to integrating them into future low emissions projects.