commutate

Commute is a verb with several related meanings, including the idea of exchanging or interchanging the order of elements in a product or sequence. In electrical engineering, commutate refers specifically to reversing or switching the direction of current within a circuit or device, often as part of a machine that uses a commutator to control current flow.

In the context of electric machines, commutation is the process that reverses current in rotor windings as the rotor turns. A DC machine uses a commutator and brushes as a mechanical switch to swap connections every half turn, turning the induced alternating current in the windings into direct current for the external circuit and producing continuous torque. Improper commutation can cause sparking, wear, or reduced efficiency. Modern drives frequently use electronic commutation—via switching semiconductor devices and pulse-width modulation—in brushless motors and inverter-fed systems, eliminating moving-contacts-based commutation.

Beyond electrical engineering, the verb commute exists in mathematics and physics, where two operators are said to commute if AB equals BA. The noun form commonly used is commutator, defined as AB minus BA, which measures non-commutativity. While “commute” is the standard term in these fields, some writers use “commutate” as a variant to describe making two operations commute or to refer to the act of commuting in a broader sense. Because “commutate” is less common in math and science contexts, readers more often encounter “commute,” “commuting,” or “commutator.”

See also: commutator, DC motor, brushless DC motor, power electronics, commutation.