The paper aims at giving a complete analytical treatment of the magnetomotive force produced by a polyphase armature winding. The fundamental principles and the scope of the investigation are enunciated in Section I. In Section 2 the magnetomotive force of a winding composed of full-pitch coils carrying sinusoidal phase-currents is investigated, and the results are applied to the case of a uniformly distributed winding in Section 3, and to a slotted armature in Section 4.The effect of the coil-span on the distribution of magnetomotive force is discussed in Section 5, and a complete generalization of all the foregoing results for currents of any wave-form is given in Section 6.