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EVO Electric Ltd. Launches New Generation of High Power Density Axial Flux Motor and Generators; Applications Include Hybrid and Electric Vehicles

Unlike radial flux motors with a cylindrical rotor turning within a cylindrical stator, axial flux motors use a disc-like rotor sandwiched between two (or facing one) disc-like stator(s)., Source: Dr. M. Lampérth. Click to enlarge.

EVO Electric Ltd., a 2007 spin out from Imperial College London, has launched its new generation of Axial Flux motor and generator technology. The new technology offers improved cost, performance and efficiency of hybrid and electric vehicle powertrains; applications include hybrid, plug-in hybrid and all-electric vehicles, range extenders, auxiliary power units (APU) and integrated starter-generator (ISG) systems.

EVO’s latest design has a demonstrated peak power density of 5 kW/kg (2.5 kg/kW nominal). (Weight measurements included all motor/generator components including housing, shaft and resolver.) Representing a 33% increase over the previous generation of EVO motors, the new generation of Axial Flux products offers the highest power density among electric motors currently available for automotive applications, according to the company.

The reported power density puts EVO’s electric machines well above the US Department of Energy’s targets for 2015 and 2020 (1.3 and 1.6 kW/kg, respectively).

EVO has performed extensive reliability, endurance, shock and vibration testing along with road tests to confirm the potential of the new motors. The machines also cost less to manufacture than other permanent-magnet motor/generators, due to their higher power and torque densities (and hence lower material costs) and a simple yet robust machine design optimized for low-cost, high-volume manufacturing.

EVO is now collaborating with automotive industry partners to develop drive systems and other products for a range of vehicle platforms. For example, EVO says it has supplied high-torque machines with peak outputs of 200 kW/660 N·m (100 kW/240 N·m nominal) and weighing only 40kg to a number of hybrid and electric vehicle developers. EVO is also developing larger models for commercial vehicle applications and an ultra-compact motor suitable for light-duty electric vehicle applications.

In 2009, EVO Electric was selected as one of the winners of the UK’s LowCVP Technology Challenge. (Earlier post.)

EVO Axial Flux motors were also featured in the Lotus Evora 414E Hybrid, a concept vehicle unveiled by Lotus Engineering at the 80th Geneva International Motor Show. (Earlier post.) The Lotus vehicle features two EVO drive motors, each providing 152 kW (207 PS, 204 hp) of power and 400 N·m (295 lb-ft) of torque, and a unique 35 kW range extender system featuring EVO’s electric generator technology.

Axial flux motors. Unlike radial flux motors with a cylindrical rotor turning within a cylindrical stator, axial flux motors use a disc-like rotor sandwiched between two (or facing one) disc-like stator(s).

Advantages to this type of motor design include higher torque density; better cooling due to higher contact area; high efficiency due to lower cooling losses; and better overload capacity.

Although the axial flux concept is not new, commercialization has been hampered by materials limitations and design tradeoffs. A number of companies and research organizations are working with axial flux technology currently (e.g., earlier post).

EVO is backed by Imperial Innovations plc, which supports scientist-entrepreneurs in the commercialization of their ideas and has exclusive access to scientific and technological developments coming out of Imperial College London.


Sanity Chk

I've been wondering when axial flux motors were going to start getting the attention they deserve.


I like this configuration, they are small, light, powerful and cheap. GM, Timken and others have had designs for a while. I am waiting for a major auto component supplier like Delphi to come up with one to reduce costs.


Interesting design with higher power density and potentially lower cost. Could be an superior candidate for many types of electrified vehicles. More torque, less weight, less cost, less cooling etc should interest many vehicle makers.

Sanity Chk

Another great advantage is the ability to stack more rotor plates to add power in a modular approach.


I question whether the energy density is worth the design tradeoffs.

The all important rotor-stator clearance is much easier to control in the radial design.

High efficiency due to lower cooling losses might mean lower efficiency but not as bad once you assume lower cooling losses.

Not a new concept, commercialization has been hampered by materials limitations and design tradeoffs.

Maybe still is.


If you read the data sheet for the small model, it is about 15 inches in diameter and 5 inches thick and is 75 kW continuous and 150 kW for 30 seconds. That is not bad for a package that size. I would have made it inductive, but that is just me.


Nice to see new EV motor designs getting the attention they should have 50 years ago. Now with the imminent move to more abundant energy - EV parts makers will wallow in the world's biggest market to date: electrification of global transportation.

bye bye petroleum...


I think that the Detroit Electric motor design done for the car maker Proton is an axial design. The video I saw showed one in a front wheel drive car with the front end covers removed. It was small for powering that car, but they claimed it would do the job.

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