shading ring

shading ring [′shād·iŋ ‚riŋ]

(electromagnetism)

The copper ring used in a shaded-pole motor to produce a rotating magnetic field for starting purposes, or used around a part of the core of an alternating-current relay to prevent contact chatter. Also known as shading coil.

(engineering acoustics)

A heavy copper ring sometimes placed around the central pole of an electrodynamic loudspeaker to serve as a shorted turn that suppresses the hum voltage produced by the field coil.