Solution of inductance for bearingless switched reluctance motor by using enhanced incremental energy method

Differing from flux linkage method and incremental energy method that need solve second-order differential coefficient, the enhanced incremental energy method (EIEM) to evaluate the flux linkage, static inductance (secant inductance) and dynamic inductance (differential inductance) for nonlinear systems is presented in this paper. After the operating point of each circuit is confirmed, a less perturbed current is applied to every circuit in the vicinity of the operating point, and then the magnetic field of the system could be perturbed. Combined with nonlinear B-H curve of magnetic materials, the magnetic incremental energy can be obtained using the integral of incremental to magnetic field H and magnetic flux density B. Hence, the flux linkage, static inductance and dynamic inductance of every circuit can be calculated without differential. Taking a bearingless switched reluctance motor prototype with 12/8 7.5 kW as an instance, mutual inductance between the phase can be neglected while the three-phase windings are considered as complete time- sharing conduct; taking linear material as an instance for iron core, the mutual inductance between the main and suspended windings can be neglected. Therefore, a solution for the static and dynamic self-inductance for the main and suspended windings of only single phase is sufficient. These inductances versus position angle and pointing current are solved, and the results are in a good agreement with the measured ones.