Saturation effects in small brushless DC motors. A simplified approach

One main point in designing small permanent magnet DC motors is to determine the operation point of the permanent magnet. This is done by a modern finite element analysis or the intersection of the linearized model of demagnetization curve with operation line, which characterizes the magnet stressing in a general case. In the latter method iron saturations are mostly neglected, but especially for small motors this simplification is no longer valid. So we present a fast method to determine the operation point of a permanent magnet with respect to iron saturation using the nonlinear iron characteristic of its permeability. Based on this approach we give an example for an already designed motor for a heart assist device and compare these results with results using a finite element analysis.