Comparative study of multi-mass models of electrical drives with asynchronous motors

The complexity of an electrical drive is such that its global study represents a difficult task at the design level as well as at the application level. To lighten this task, it is common practice to perform some simplifications; linearization of some characteristics, lumping of the distributed inertia of mobile parts with that of the motor rotor, etc. Because of the finite stiffness in the links between different parts of the mechanism in some types of drive (mills, large mobile structures, flexible robotic limbs, etc.), it becomes important to realize a multi-mass model of such a mechanism. This paper is about the elaboration of a refined model of an asynchronous motor drive, which takes into account the flexible links between the different parts of the load mechanism. First, a theoretical analysis is presented of the asynchronous motor and the load mechanism; second, a comparative analysis, based on numerical simulations accomplished with MATLAB/SIMULINK, is performed on drive models with one, two or three masses; then drive startup and the application of a step load are shown in the simulations; and finally, observations and comments are given about the benefits of such refined models.