Effects of Mechanical Resonance on Vibrations of Mechanical Systems With Permanent Magnet Machines

In this paper, we describe the effects of mechanical resonance on the vibrations of mechanical systems with permanent magnet (PM) machines. Electromagnetic vibration sources produced by a PM machine were calculated using finite element analysis (FEA) solutions. Subsequently, the harmonic orders related to the mechanical vibrations of the PM machine itself were investigated experimentally by driving the machine at various rotor speeds. To investigate the effects of mechanical resonance, a cantilever beam whose mechanical resonance frequency can be changed by adjusting its length was employed. Finally, the resonance condition was achieved by matching the natural frequency of the cantilever beam with the vibration frequencies produced by the PM machine. The natural frequency mode shapes were validated using 3-D FEA solutions, and the results were confirmed through modal analyses of the frequency response function results from impact tests. Comparisons of the measured vibration data of the PM machine with and without the cantilever demonstrated that mechanical resonance significantly influenced the vibrations of mechanical systems using PM machines.