Design of a reluctance synchronous machine for an electric vehicle with a multi speed gearbox

[摘要] ENGLISH ABSTRACT: Conventional electrical vehicles (EVs) favour mostly permanent magnetmachines with single speed gearboxes. This is understandable, the PM machinehas a high power density making the electrical machine smaller in size.The PM machine also has a favourable field weakening capability combiningthis with a single speed gearbox nearly perfectly matches the required tractioncurve. However the dependency of rare earth metals from China and theenvironmental issues raised by mining these metals raise concern. Thereforealternatives should be considered. Induction -, switch reluctance - and woundrotor machines are all gaining ground as favourable traction machines to powervehicles. The reluctance synchronous machine (RSM) is known for it's robustnessand high efficiency, however the machine has a limited field-weakeningcapability. To overcome this short coming a multi gearbox from an internalcombustion engine (ICE) is suggested.By combining the RSM and multi speed gearbox it is possible to match thetraction curve. There are numerous advantages offered by using this system,especially from an performance and efficiency point of view. However thereare also numerous challenges faced by using the suggested powertrain, howeverthe focus of this study is mainly on performance and efficiency of the motorand the powertrain.As a case study a Corsa 140i is used and the design specifications is takenfrom the ICE. The aim is to design a RSM that meets the specifications ofthe ICE. The RSM structure is mathematically modelled then optimized usingcommercial optimization and 2D finite element software. To evaluate the design of the RSM, the motor is then tested. The powertrain is then tested byconnecting the motor onto the gearbox of the Corsa and the efficiency of thepowertrain is evaluated.The test results it shown that the RSM can be used as a traction motor.There are two motors built one with NO20 and the other with M530-65Alamination steel. Both motors perform well throughout the speed and torquespectrum. The measured efficiency at the rated condition for the motor withthe NO20 steel is above 91% and the motor with the M530-65A laminationsabove 89%. The power train is is tested in 4th and 5th gear. The efficiency of4th and 5th gear is approximated and the efficiency is above 90% . This highefficiency makes the multi speed gearbox a competitor for the EV power train.

[发布机构] Stellenbosch University