An Investigation of Electric Motor Drive Characteristics for EV and HEV Propulsion Systems

Electric Motor Drive Selection Issues for HEV Propulsion Systems: A Comparative Study

“…The major requirements of HEVs electric propulsion, as mentioned in past literature, are summarized as follows [1], [3]: 1) a high instant power and a high power density; 2) a high torque at low speeds for starting and climbing, as well as a high power at high speed for cruising; 3) a very wide speed range, including constant-torque and constant-power regions; 4) a fast torque response; 5) a high efficiency over the wide speed and torque ranges; 6) a high efficiency for regenerative braking; 7) a high reliability and robustness for various vehicleoperating conditions; and 8) a reasonable cost. Moreover, in the event of a faulty operation, the electric propulsion should be fault tolerant [10], [11].…”

“…This profile is derived from the characteristics of the power source and the transmission. Basically, for a power source with a given power rating, the profile of the tractive effort versus the speed should be a constant power in the speed range, and then, the tractive effort drops hyperbolically with the increase of the vehicle speed [1], [3]. It should be noted that these characteristics depend on HF.…”

“…Any attempt to operate the motor at the maximum current beyond this speed will stall the motor. Moreover, efficiency at a highspeed range may suffer in addition to the fact that IMs efficiency is inherently lower than that of PM motors, due to the absence of rotor winding and rotor copper losses [1].…”

“…However, these motors inherently have a short constant-power region due to their rather limited field weakening capability, resulting from the presence of the PM field (the fixed PM limit their extended speed range) [ Fig. 12(a)] [1]. In order to increase the speed range and improve the efficiency of PM brushless motors, the conduction angle of the power converter can be controlled at above the base speed.…”

“…In fact, the choice of electric-propulsion systems for HEVs mainly depends on three factors: driver expectation, vehicle constraint, and energy source. With these considerations, it is obvious that the overall motor operating point is not tightly defined [1]. Therefore, selecting the most appropriate electric-propulsion system for a HEV is a challenging task.…”