Combined Model for Simulating the Effect of Transients on a Damaged Rotor Cage

Comparison of thermal stresses developed during transients on a damaged rotor cage

“…A rigorous attempt to study it, especially needed if the secondary circuit is asymmetric, would yield that most, if not all, phenomena are tightly coupled, making the problem intractable. Therefore, the strategy followed in [9] has been to combine analytical and FE methods using the advantages of Elmer FE software [13] whilst assuming a direct coupling of distributed parameters just for the variation of conductivity with temperature.…”

“…As introduced in [9], for the computation of the electromagnetic state of the machine an analytical model is used. Finite element analysis and a thermal network yield the thermal state of the rotor and stator, respectively.…”

“…The aim of this work is thus to extend the results presented in [9] by comparing the thermal and mechanical effects on a damaged rotor cage (featuring a hot spot or narrowing of one of the bars) during several kinds of transients and different sizes of the defect. The original section of the bar is reduced to 12%, 8% and 4% and startup, plug stopping and stall operation modes are examined, this later considered the most damaging since there is no end space and air gap ventilation [12].…”

“…Following [1,7,8] and within the Condition-Based Maintenance and Prognostics and Health Management (CBM/PHM) architecture, [9] proposed a combined approach to simulate the effect of hot spots in the rotor cage by computing analytically the electromagnetic behavior of the motor and then reproducing the calculated currents in the cage on a 3D mesh representing half of the rotor. The yielded current distribution (only taking into account the resistances of the rotor elements) was used to obtain the heating and the temperature distribution, whilst thermal effects arising from magnetic phenomena were imposed on the mesh from independent analytical computations.…”

“…The effect of a possible straightforward mitigation method is also simulated. For this purpose, the rest of the paper is organized as follows, Section II gives an overall description of the combined model used here, already introduced in [9], Section III presents the simulation's details, Section IV shows the results and Section V yields the conclusions.…”