commutated

Commutated is the past participle of commutate, meaning that something has undergone the process of commutation. In electrical engineering, commutation refers to the switching of current in a circuit or the reversal of current in a winding at a specific time. The term is used to describe devices and machines that rely on this switching action for their operation.

In electric machines, commutated machines use a mechanical commutator to reverse the current in rotor windings as the machine rotates. This reversal maintains torque in a single direction and enables direct-current (DC) operation. The commutator is typically a segmented cylindrical surface on the rotor, contacted by stationary brushes. Brushed DC motors and universal motors are described as commutated machines. The quality of commutation affects sparking, wear, efficiency, and noise; design choices such as winding arrangement, slotting, and brush materials influence performance.

In power electronics, commutation also refers to turning current on or off in switching devices. For thyristors and similar components, natural commutation occurs when the supply current falls to zero, while forced or load-commutation uses auxiliary circuitry to interrupt current. In relays and contactors, commutated switching denotes the deliberate transfer of current paths as contacts actuate.

Limitations and considerations: Commutation can cause arcing at the brush-commutator interface, leading to wear, EMI, and reduced lifespan. Advances include improved commutation schemes, brushless designs that eliminate mechanical commutation, and alternative switching devices that minimize or remove the need for commutation.