General presentation
DC machines - Constitution and operation

Throughout this article, we'll be using the Laplacian model, which consists of reducing the conductors to the periphery of the air gap in the form of fictitious surface currents. This approach is less rigorous than variational analysis with equivalent magnets, but it provides a simple description of all the main and secondary phenomena governing these machines.

From a structural point of view, a DC motor comprises a rotating armature and a fixed inductor. The latter part can be either wound or made with permanent magnets. We'll start our study with a simplified motor of the latter type.