ABSTRACT

EV share is steadily increasing as the battery cost reduces and power density increases. For vehicle drive, the motor should have a high starting torque and produce high power during high speed. Internal combustion engines (ICEs) are limited in the working range in comparison to electric motors. For example, ICEs cannot produce torque at zero speed, and its efficiency drops quickly with speed. These restrictions are solved by gear shift and slip mechanism. Gear shift offers several torque-speed curves as shown in Fig. 12.1. On the other hand, electric motors have a large starting torque, and can work over a wide speed range. EV motors are normally used without a gear shifting mechanism. The EV range (dotted line) is compared with multiple torque-speed curves of ICE in Fig. 12.1.