Patent attributes
It is an object of the invention to provide an improved technique for controlling the output characteristic of a motor. Representative power tool includes a tool bit and a motor. The motor drives the tool bit and includes an armature, a coordinator, a plurality of segments and a plurality of armature windings. The armature has a plurality of slots. The communicator rotates together with the armature. Plurality of segments is provided on the communicator. Respective armature windings are connected at the both ends of the segments. Each of the armature windings is defined by coils that are wound between respective pairs of the slots of the armature. Each of the armature windings is formed by at least two coils connected in series. At least one of the coils defining the armature winding has a different number of turns of a wire wound between the associated slots from the other coils in the same armature winding. On the same time, the total number of turns of the coils of each of the armature windings is the same. Thus, as a result, the magnetic field around each of the armature windings can be kept substantially the same while providing fine adjustment of the numbers of turns in the armature windings.
