Armature

Armature, in electrical engineering, the term applied to a very important part of the modern dynamo or motor, on the construction of which the efficiency of the machine largely depends. The theory of the armature is explained in the article Dynamo-electric Machinery. It consists essentially of an arrangement of coils of wire or metallic riband so wound as to aim at producing a great difference of potential in the circuit, when rotated at a definite rate in the magnetic field. The coils are wound on some sort of soft iron core, inasmuch as this increases the intensity of the magnetic field.

Siemens introduced in 1856 a core of H-shape,. shuttle-wound; Gramme invented in 1870 a ring-shaped iron core, the wire being wound round this in a particular way. Modifications of these two are the chief forms of core used at present. To wind the wire in such a way as to give a great number of coils, and to pack them in the most intense part of the magnetic field, affords much scope to the inventor. Hence the methods of winding are very numerous.