Nonlinear effects on the rotor driven by a motor with limited power

Abstract

Rotating machines are complicated systems consisting of rotor, stator, driving motor, electric feeding system, etc. Such structures contain many kinds of nonlinearities, both in mechanical and electrical parts. Computing model of the studied system has 4 DOF and the main nonlinearities that are considered are those generated by the driving properties of limited power source and nonlinearities of electric part of motor. Effect of non-ideal source of excitation energy was studied e.g. in [1–5]. Nonlinearities of rotor supports were investigated e.g. in [3, 6]. Here we focus on the influence of nonlinear magnetic flux, with weak smooth nonlinear characteristics. Rotor and its supports are considered as linear. After derivation of differential equations of motion, the effect of different values of nonlinearity of magnetic flux on the mechanical vibration of rotor, on fluctuation of angular velocity and on variation of driving current at constant feeding voltage and at constant loading moment is studied by numerical solutions. Results are presented in the form of time histories and of plane trajectories of main motion variables.