Efficiency impact of motor type and motor size choice

Report, 2021

Permanent magnet synchronous motors are often used in drive trains for electric and hybrid vehicles. At the Division of Electrical Engineering at Chalmers University of Technology several works on different machine types as traction motor have been done. Radial flux machines of
different sizes , axial and transversal machines have been investigated. Together with the department of Environmental Systems Analysis, the different motors have also been objects for LCA calculations.
This report investigates high power cars that often use one machine per wheel axis. The radial flux machines with 8-poles and different sizes have been evaluated. As an alternative to two permanent magnet machines one of them are exchanged to a reluctance machine. With the reluctance machine
it’s possible to keep that machine rolling without iron core losses and only use it when needed for acceleration. The high speed performance is quite low but it can save a lot of losses during normal operation.
The losses over the WLTP drive cycle is halved, when using the reluctance and PM combination, compared to a solution with two permanent magnet machines and the same gain can be seen when compared to one big permanent magnet machine. The gain at highway speed seems to be lower but
still there are efficiency gain to be done.