This paper describes a theoretical analysis of a self-excited wound-field synchronous motor in which space harmonics power is utilized for field magnetization instead of permanent magnets. The operation principle of the proposed motor can be explicated by a voltage equation on the synchronous rotating reference frame. The effect of an auxiliary pole designed to be magnetically independent of the main magnetic flux path and placed on the q-axis is mathematically discussed, and is analytically investigated through FEM based computer simulations.