Measurement of flux linkage in the hybrid stepping motor drive

In its most common form, an electrical machine converts energy from electrical to mechanical or vice versa via a coupling magnetic field. Flux linkage is a parameter which describes this coupling characteristic. Measurement of flux linkage in an electrical machine is useful for validation of the design model as well as for control purposes. In a singly excited system, the measurement of flux linkage is often obtained by integrating the terminal measurements of the phase winding circuit. In a doubly excited system, the measurement of flux linkage is complicated by the presence of another MMF source. In this paper, the theory of flux linkage measurement in a doubly excited system is presented and a method is described which allows measurement of the flux linkage in a hybrid stepping motor in which one of the MMF sources is the permanent magnet on the rotor