The Effects of Structural and Localized Resonances on Induction Motor Performance

Troubleshooting resonance problems within alternating current induction motor systems has always presented difficult challenges for motor manufacturers and end users alike. Often, the changes in structural stiffness from a motor manufacturer´s rigid foundation to a less stiff field base can produce drastically different vibration performance. In most cases, a structural natural frequency of a motor or foundation that coincides with a motor forcing function will provide detrimental results to the motor vibration. Many times the effects of undesirable system resonances may be detected after the motor has been installed, causing costly down time, or even motor failure if the problem remains undetected. Additionally, natural frequencies of motor components, such as fans, may cause a catastrophic fatigue failure when the motor is subjected to forcing functions with frequencies in the vicinity of these localized resonances. This paper will provide insight on motor system resonances and localized resonances that may be damaging to an induction motor´s operation.