Electric Motors, Made to Order

The electric motors that drive today’s hybrids and electric vehicles are not so different from those pioneered by Nikola Tesla and George Westinghouse a century ago.

Like their predecessors, modern electric machines, to use the engineers’ preferred term, are composed of two elements: a fixed housing that contains copper wire wound around an iron core, called the stator, and a rotor that spins within the stator’s open center.
The interaction of electric current and magnetic fields between the stator and rotor create rotational torque to spin the motor’s shaft — and turn the wheels.

Tailoring electric motors for duty in vehicles has necessitated the development of new materials, sophisticated electronic controls and some clever design variations, said Heath Hofmann, an associate professor of electrical engineering and computer science at the University of Michigan in Ann Arbor.

“The auto companies are focusing on machines capable of operating over a much wider speed range than typical fixed-speed industrial motors,” he said. Two primary designs for electric machines, A.C. induction and permanent-magnet, prevail in today’s hybrids and E.V.’s. They differ mainly in the construction and operation of their rotors.

New York Times