Lateral Superharmonic Resonance of the Rotor in 12/8 Poles Switched Reluctance Motor

Abstract

Switched reluctance motor (SRM) generates a very large electromagnetic radial force when the stator windings commutate because of its doubly salient structure and magnetic saturation. Lateral vibration appears when electromagnetic radial force is applied onto the rotational rotor, which causes continual changes of airgap and further radical electromagnetic force. Nonlinear vibration of the rotor under the interaction of electromagnetic radial force and displacement becomes very complicated, which is becoming a research hotspot at present. A whole lateral vibration dynamics equation is established by finite element method. The radical force formula of single rotor tooth was deduced by integration of equivalent electromagnetic circuit and Maxwell stress method, and final functional expression of radial electromagnetic resultant when stator windings are energized with ideal square wave is also obtained. The critical speeds and vibration modes of the rotor are analyzed by Campbell diagram and lateral vibration displacement locus is solved by Newmark-Beta numerical integration method. The results show that the vibration locus of the rotor distributes in a circular domain. The frequency distribution of electromagnetic resultant relates to rotation speed, current switch frequency, and current wave, while the frequency distribution of the displacement also closely relates to the first-order critical speed of the rotor. When the rotor runs at some specific speed, lateral superharmonic resonance phenomenon appears and its displacement locus shows rich diversity. Lateral vibration characteristic of the rotor could be quickly grasped through this study, which makes vibration evaluation possible for advanced motor design.