An algorithm for analysis of magnetic co-energy stored in permanent magnets

The principle of virtual work is now used as a matter of routine to compute the electromagnetic force/torque. However, the absence of clear calculation method of the co-energy stored in permanent magnets has limited its applications in permanent magnet systems. In this paper, a novel algorithm of the co-energy stored in permanent magnets is proposed and the corresponding physical meanings are clarified. In addition, the correctness of the derived formulation is confirmed by an example. Based on them, the applicability of the method is investigated considering practical demagnetization characteristics, and moreover, the overall co-energy of a permanent magnet system is also presented using both analytical method and graphical method. All the above has provided theoretical foundation for the virtual work method and can widen its area of application to a certain extent.