VIBRATION MODES AND ACOUSTIC NOISE IN A 4-PHASE SWITCHED RELUCTANCE MOTOR

Acoustic noise in the switched reluctance motor (SRM) is caused primar ily by the deformation of the stator lamination stack, Acoustic noise is most severe when the periodic excitation of the SRM phases excites a natural vibration mode of the stack, The natural vibration modes and frequencies of a four phase, 8/6 SRM are examined, Structural finite element analysis is used to compute the natural modes and frequencies. Impulse tests on the stator stack verify the calculations and show wh ich modes are excited, Heuristic arguments are developed to predict th e operating conditions that will excite the natural modes, Measurement of vibration while the machine is under load shows which operating co nditions excite the natural modes and verifies the predictions, An app roximate formula is derived to predict the frequency of the fundamenta l vibration mode in terms of lamination dimensions and material proper ties, The formula is validated by comparison with finite element calcu lations for several laminations, and hence is shown to be useful in de sign trade-off studies.