The market of electric vehicles (EVs) is rapidly growing across the world attributed to their unique feature of zero carbon emission. Take
the Chinese market as an example, 984,000 pure electric vehicles were sold in China in 2018, which is an increase of 50.8% over the same
period of the previous year. This means there will be more and more electric vehicles will run on the road in the future. However, the
reliability of these electric vehicles is still an open issue remaining to resolve today. In particular, the reliability of the motor controller in
electric vehicles is receiving more concern than ever before. On the one hand, this is because it is well known that power electronic
components in the controller are much less reliable than the mechanical components in other EV subassemblies. One the other hand, it is
because the failure of motor controller may lead to dangerous accidents on the road. Previously, much effort has been made to try to
predict the reliability of motor controller, however detailed investigation of its reliability issues has never been done before. In view of
this, a detailed reliability study of the motor controller in pure electric vans will be conducted in this paper, with the consideration of the
fact that more than 90% of sold commercial electric vehicles are pure electric vans. In the research, the detailed root causes of the
reliability issues in the motor controller will be investigated first and then based on which the failure rates of individual components (e.g.
control module, driver module, communication module, and discharging module) in the controller will be estimated with the aid of fault
tree analysis and the international standards IEC TR62308-2004, MIL-HDBH-217E and the technical standards for the Chinese electric
vehicle industry. Finally, the tendency of the unreliability index of the entire motor controller against the service life of the electric vehicle
is estimated based on the fault tree analysis results in order to obtain a more reliable understanding of the reliability performance of the
motor controller over time. From such detailed reliability research, it has been found that the reliability performance of the motor controller
will degrade gradually over time; and among the four functional modules of the controller the control module is most vulnerable, followed
by driver module. This could be due to the application of more electronic components and thinner printed lines on the module