Compact Wheel Direct Drive for EVs

The envisaged introduction of electrical vehicles (EVs) in the market will open a large application area for electrical motor drives, and such a prospect is drawing considerable attention and substantial international activity toward the development of electrical motor drives that allow an improvement in the performance of EVs. Among a number of drive arrangements under investigation for application in EVs, one advantageous solution consists in the use of a low-speed electrical motor coupled directly to the wheel axle to eliminate the mechanical power transmission system otherwise required. Advantages resulting from such a drive arrangement are a significant reduction of the vehicle weight and an improvement in the drive's overall efficiency. However, the wheel direct drive application requires the use of low-speed motors having a very high torque-to-weight ratio and efficiency to limit the ma ss stressing the wheel suspension and really gain the benefits envisaged in terms of drive efficiency.