Somewhere in most engineering educations, there’s a class on induction motors. Students learn about shaded-pole motors, two-phase and three-phase motors, squirrel cage motors, and DC-excited motors.

A synchronous and synchronous motors are the two main categories of ac motors. The induction motor is a common form of asynchronous motor and is basically an ac transformer with a rotating secondary.

Continuing headlines about superefficient electric drives might lead some observers to wonder about the future of three-phase induction motors. The truth is that induction motors aren’t going away any ...