tailieunhanh - Electric Vehicles Modelling and Simulations Part 3

Tham khảo tài liệu 'electric vehicles modelling and simulations part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Control of Hybrid Electrical Vehicles 49 4. Electric motors used for hybrid electric vehicles propulsion Motor characteristics versus electric traction selection The electric motors can operate in two modes a as motor which convert electrical energy taken from a source electric generator battery fuel cell into mechanical energy used to propel the vehicle b as generator which convert the mechanical energy taken from a motor ICE the wheels during vehicle braking etc. in electrical energy used for charging the battery. The motors are the only propulsion system for electric vehicles. Hybrid electric vehicles have two propulsion systems ICE and electric motor which can be used in different configurations serial parallel mixed. Compared with ICE electric motors has some important advantages they produce large amounts couples at low speeds the instantaneous power values exceed 2-3 times the rated ICE torque values are easily reproducible adjustment speed limits are higher. With these characteristics ensure good dynamic performance large accelerations and small time both at startup and braking. Fig. 5. a. Characteristics of traction motors b. Tractive effort characteristics of an ICE vehicle Figure illustrates the standard characteristics of an electric motor used in EVs or HEVs. Indeed in the constant-torque region the electric motor exerts a constant torque rated torque over the entire speed range until the rated speed is reached. Beyond the rated speed of the motor the torque will decrease proportionally with speed resulting in a constant power rated power output. The constant-power region eventually degrades at high speeds in which the torque decreases proportionally with the square of the speed. This characteristic corresponds to the profile of the tractive effort versus the speed on the driven wheels Figure 5. b. . This profile is derived from the characteristics of the power source and the transmission. Basically for a power source with a given power rating