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This paper deals with the quenching problem of electromagnetic vibration of the motor stator in the wide frequency region around the natural frequency using two dynamic absorbers. The iron stator of motor is modeled by circular ring, and two dynamic absorbers are installed on the outside of iron stator to quench the forced vibration caused by the rotating distributed electromagnetic force. The solutions of forced vibration are obtained by the theoretical analysis, and those are compared with the solutions obtained by the finite element method and numerical integration. Following was made clear: (1) By installing two dynamic absorbers which have not only different natural frequencies and different damping ratios but also different masses each other, the iron stator is quenched better than by installing the same dynamic absorbers. (2) It is possible to obtain nearly optimum quenching effect with a pair of dynamic absorbers with equal masses. (3) The mechanism of the above-mentioned vibration quenching method using two different dynamic absorbers is made clear. (4) In the case using the dynamic absorbers those have small values of damping ratios, about 25 degrees is better as angle made by the two dynamic absorbers. (5) The characteristics of resonance curves obtained by the theoretical analysis using ring theory and those obtained by the finite element method and numerical integration agreed well each other.

This paper deals with the quenching problem of electromagnetic vibration of the motor stator with imperfections at the resonant frequency using a pair of dynamic absorbers. The iron stator of motor is modeled by a circular ring with single or two imperfect masses, and dynamic absorbers are installed on the outside of the circular ring to quench the forced vibration caused by the rotating distributed electromagnetic force. The solutions of forced vibration are obtained by the theoretical analysis. The following were made clear; (1) As imperfect mass reduces the natural frequency of the motor stator, resonant frequency becomes low. (2) In the case where the weight of two imperfect masses are heavy, the closer the angle at which two imperfect masses forms, is close to the angle between the loop and node of the mode that is to be quenched, the resonant amplitude is reduced. (3) By installing single dynamic absorber and single imperfect mass, and by setting an angle between the loop and node of the mode to be quenched, quenching is possible. (4) Even if imperfections exist, installing a pair of dynamic absorbers that make an angle equal to the one between the loop and node of the mode to be quenched, makes the motor stator quenched perfectly.

This paper deals with the quenching problem of electromagnetic vibration of the motor stator in the wide frequency region around the natural frequency using multiple dynamic absorbers. The iron stator of motor is modeled by circular ring, and a pair of dynamic absorbers or two pair of them are installed on the outside of the circular ring to quench the forced vibration caused by the rotating distributed electromagnetic force. The solutions of forced vibration are obtained by the theoretical analysis. Following was made clear: (1) By installing two dynamic absorbers those have the same appropriate natural frequency ratios and damping ratio, the iron stator is quenched well. (2) By installing the same two dynamic absorbers leaving an angle that is equals to the one between loop and node of the mode to be quenched, the iron stator is quenched best. (3) By installing the two dynamic absorbers those have different natural frequency ratios and damping ratios each other, the quenching effect become a little better than the case mentioned above. (4) By installing the multiple pair of dynamic absorbers, the quenching effect become much more better than the cases using a pair of dynamic absorbers.