A thermal transient finite-element study to connect suitable loads to an induction motor

The transient thermal behaviour of a squirrel-cage induction motor which has to drive ventilators having a gyratory moment different from that of the rated ventilator in consequence of a mechanical fault of the latter has been studied in a previous paper. The aim of the present paper is to evaluate the air flow of each ventilator in correspondence with which the thermal stresses of the induction motor, calculated by the finite element method, must not exceed the limits values fixed by standards. The ventilators are assumed to be homothetic between them and the transient thermal analysis on the induction motor is carried out by a finite-element package entirely developed by the authors. The paper aims at determining, for each ventilator, the maximum number of duty cycles per hour which the induction motor can perform and, consequently, the flow rate conveyed which must obviously be close to that of the rated ventilator.