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The interior permanent magnet (IPM) motor has been popular in both hybrid and fuel cell electric vehicles due to its high efficiency, high torque density and low phase current. Automobiles require both a wide speed range and low power consumption. Peak torque per ampere, regenerative braking and constant power range are critical to maximizing overall vehicle efficiency. Improved control techniques show better performance for vehicle application (limited power source, rapid response of speed and torque). During flux-weakening, a bottom line of maximum torque current is set and controlled. For smooth torque control, flux current is regulated by torque current rather than torque.

The electric motor plays a critical role for the applications of the Hybrid Electric Vehicle and Fuel Cell Electric Vehicel. It is also well known that thermal constraints represent one of the main limitations in the performance of the electric motor. For example, the electric motor will be short-circuited if the insulation coatings of the copper wire bundles fail. Furthermore, the performance of the permanent magnet electric motor reduces significantly as the rotor magnet temperature increases. In this study, a series of Computational Fluid Dynamics analyses were performed for the design of a liquid-cooled permanent magnet electric motor to achieve better thermal performance. Several thermal tests of a partial permanent magnet traction motor assembly (stator and housing only) were also performed to determine effective properties of the stator slot and thermal contact resistance between stator and housing that may vary due to the manufacturing process. A simplified thermal network model of this system was established from the Computational Fluid Dynamics analyses. Then the critical heat transfer path of this system was identified.Copyright © 2003 by ASME