Axial flux machine as a traction motor for electric and hybrid vehicles
Permanent magnet synchronous motors are often used in drive trains for electric and hybrid vehicles. The Division of Electrical Engineering at Chalmers University of Technology have done a work on different radial flux machines as traction motor. As a compliment axial flux machines are also added to the comparison. Together with the department of Environmental Systems Analysis, the different motors have also been objects for LCA calculations. The radial flux machines have 8-poles and different magnet material have been evaluated. Compared to the radial flux machines a 16-pole axial flux machines have lower material weight but also lower efficiency. The high speed performance are also quite low, but an yokeless variant can have as high maximum efficiency as the best machines and about 50 % of the weight compared to the radial flux machines. The maximum efficiency is reached at higher torque compared to the radial flux machine so the overall efficiency over a drive cycle is lower for the axial flux machine. A solution with iron powder material has generally higher losses but if the iron core is made of high grade material and the size of the machines is changed, there is a possibility to make a good machine for propulsion of electric vehicles.