Abstract
Thermal stress of the rotor in a squirrel cage induction motor is generated due to the temperature rise, it is also one of the factors causing the broken bar fault because the structure of the rotor would be destroyed if the stress of the rotor bars exceed the strength limit. The coupled fluid-thermal analysis for the induction motor with healthy and broken bar rotors is performed in this paper. Much concern has been committed to establishment of the fluid model on the basis of computational fluid dynamic (CFD) theory. The heat field of the prototypes is analysed so that the effect of the asymmetrical rotor on the motor heat performance can be investigated in depth. Eventually, the efficiency of the presented model and method, for the totally enclosed fan cooled (TEFC) induction motor, can be verified through experimental results. In addition, this paper reports a quantitative analysis of the heat flux distribution of the fault rotor, and the heat flux density of the bars is investigated in detail. Then, the part most likely to break in the rotor as a result of the thermal load is identified.
Highlights
As a key performance parameter of electrical machines, the temperature rise has been of wide concern in the industrial field
The accuracy of thermal analysis greatly depends on the heat transfer coefficient on heat transfer surfaces, so it is essential for designers to get an accurate analysis of the fluid field
As well known the losses, in an induction motor bring about the temperature rise, which can cause cause significant thermal stress, and the total losses of the motor can be given by the following significant thermal stress, and the total losses of the motor can be given by the following Equation [26]: Equation [26]: P = PPcu
Summary
As a key performance parameter of electrical machines, the temperature rise has been of wide concern in the industrial field. Inner and outer environment of the motor is complex, in some conventional methods [5,6,7], the fluid model is usually simplified, or the fluid velocity on heat transfer surfaces is regarded as constant, so the corresponding heat transfer coefficient is constant These studies provide good ways to fluid field analysis, but the continuity of the fluid field distribution is not included. The CFD (computational fluid dynamic) analysis and the thermal equivalent circuit model have been established for a totally enclosed fan cooled (TEFC) induction motor, and the simulation data are compared with experimental data measured by sensors [12]. The calculated results are close to the experimental data, and the analytical method in the paper proved to be valuable can provide references for the other middle and small induction motors
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