Effect on Vehicle Performance of Extending the Constant Power Region of Electric Drive Motors

The effect on vehicle performance of extending the constant power operating mode of electric drive motors for electric and hybrid vehicles is presented in this paper. Modern electric and hybrid vehicle designers have the selection of several technologies to choose from when selecting an electric drive motor. Each motor technology exhibits a particular torque vs. speed characteristic. Many of these technologies, most notably the switched reluctance machine, have capitalized on iron and copper utilization, extending their useful speed range. However, the extended speed capabilities of these motor drives have vehicle performance consequences.

It is presented that vehicle performance is affected by changing the torque-speed characteristics of the drive motor. The extended constant power speed range motor can have smaller rated power than otherwise but suffer high speed passing performance. Traditional extended constant power range motors (about two times the rated speed) have to have a higher rated power but exhibit superior performance capability.