Armature coil slots having grooves formed in its throat

摘要

An armature for a d. c. motor comprises a shaft, a commutator, a coil and an armature core having a plurality of slots at its circumference to receive the coil. The opening portion of the slots is made smaller than the diameter of a wire constituting the coil, and a groove and a coil constraining portion are formed in a throat portion between the opening portion and a coil receiving portion formed in the slot.