Effect of the non‐linearity of demagnetization curves on the torque of hybrid stepping motors with permanent magnets in slots

The recent achievements in electronic control as well as the higher performance of advanced permanent magnets have brought about a change in the general strategy for design and development of new types of small electrical machines. A special application of permanent magnets (PM) is represented by hybrid stepping motors (HSM). The latter are a sort of combination of variable reluctance‐motors and permanent magnet‐motors. The influence of various PM inserts into the magnetic circuits of electromechanical converters on field and force distribution has been already investigated by the authors (1996). Promising results for HSM have been reported, especially when rare‐earth PMs are used. The main aim of PM inserting, when they are put into slots of slotted pole shoes with radial N‐S polarization, is to focus magnetic field lines in the corresponding teeth. As a result, the reluctance stepping torque can be increased depending on the material used. Now a further step is made by extending the analysis from the case of linear to that of non‐linear demagnetization curves of permanent magnets.