Design of copper rotor induction motor for mild-hybrid electric vehicle

Abstract

With the advent of NEMMP (National Electric Mobility Mission Plan), increase in both production and demand of hybrid and electric vehicles is expected in coming years. Mild hybrid vehicles (MHV) are sought as one of the most plausible options among alternative-fuel-vehicles. There are two prime goals behind development of MHV — a) increase in fuel efficiency and thereby reducing emissions b) keeping incremental cost as low as possible when compared to IC engine vehicle. A car-segment vehicle is considered as pilot-vehicle for the present work. In the pilot-vehicle, electric power is used for threefold applications — a) eliminating idling energy losses with regenerative braking b) engine cranking and c) assisting engine during peak power demand. Induction motor offers a cost-effective solution suitable for the application, due to its ruggedness and established control strategies. Further, use of copper cage in rotor yields higher torque for given input current, which is necessary for assisting engine cranking and peak power mode. As the motor is packaged in high-temperature-environment in the pilot vehicle, forced water cooling is provided. This allows reduction in size of the motor by around 30%. To this end, this paper will elaborate on FEA (Finite Element Analysis) — based design process followed and experimental results. Suitability of this motor to its application by means of simulation of motor performance for several drive cycles, will also be discussed.