Vibration analysis and reduction in switched reluctance motors

A detailed normal force vs. phase current and rotor position look-up table for a switched reluctance motor is constructed using Finite Element calculations. Subsequently, a normal force vs. stator acceleration transfer function is determined in this dissertation based on sinusoidal shaker excitation tests. A vibration prediction model of the SRM is built based on the transfer function and normal force look-up table. The model is verified by motor tests, which show acceptable accuracy. This now allows the possibility of using a transfer function model, such as this, for improved design of SRMs from vibration and acoustic noise points of view.; Simulation models based on Matlab/SIMULINK are developed in this dissertation, which can be used to simulate the transient phase current response, normal force and hence stator vibrations during accelerating, sudden change of torque and braking operations. An 8/6 SRM is used to experimentally validate the simulation results of both phase current and stator vibrations. The simulated phase currents are used in the previous described vibration prediction model to calculate the vibrations in different SRM operating conditions: constant speed running, accelerating, sudden change of torque and braking.; The effects of mountings on the vibrations in the SRM are investigated, using Finite Element calculations and impulse hammer test results. The calculated and test results are compared with each other to verify if the methods developed are valid in the research of SRM vibrations under various mounting conditions. Firstly, the finite element method is used to calculate the resonant frequencies for free vibrations and different mounting conditions: free hanging, foot-mounted and face-mounted (with mounting feet and without mounting feet). Secondly, vibration tests are done with different mountings, and the results summarized in the form of mounting guidelines.; Some experimental methods other than sinusoidal shaker excitation tests are introduced in this dissertation, which include white noise shaker excitation tests and impulse hammer tests. The white noise shaker tests can be used to identify the mode shapes of the motor stator and locate the resonant frequencies. Practical measurements of mode shapes using this method are described. The 2nd and 3rd mode resonant frequencies and mode shapes for free vibration are measured and compared with FE results, which show good correlation. The impulse hammer tests are described and the advantages and disadvantages when compared with shaker excitation are discussed.; Techniques for noise reduction require knowledge of the modal frequencies, which depend on Young's modulus. This dissertation introduces a simple and nondestructive method for the measurement of Young's modulus, which is then used in a finite element program to determine the resonant frequencies of SRM stator vibration. The FE results are validated by impulse force hammer tests. Some other material properties like Poisson's ratio, winding effects and stator core lamination stacking factor are also examined.