Abstract
In a traditional lumped-parameter thermal network, no distinction is made between the heat and non-heat sources, resulting in both larger heat flux and temperature drop in the uniform heat source. In this paper, an improved lumped-parameter thermal network is proposed to deal with such problems. The innovative aspect of this proposed method is that it considers the influence of heat flux change in the heat source, and then gives a half-resistance theory for the heat source to achieve the temperature drop balance. In addition, the coupling relationship between the boundary temperature and loading position of the heat generator is also added in the lumped-parameter thermal network, so as to amend the loading position and nodes’ temperature through iterations. This approach breaks the limitation of the traditional lumped-parameter thermal network: that the heat generator can only be loaded at the midpoint, which is critical to determining the maximum temperature in asymmetric heat dissipation. By adjusting the location of heat generator and thermal resistances of each branch, the accuracy of temperature prediction is further improved. A simulation and an experiment on a U-core motor show that the improved lumped-parameter thermal network not only achieves higher accuracy than the traditional one, but also determines the loading position of the heat generator well.
Highlights
Thermal analysis is extremely important for the electrical machine design, because overheating will accelerate insulation aging, demagnetize permanent magnets, and even cause system failure [1].In general, there are three kinds of method for thermal analysis; i.e., the finite element method (EFM), computational fluid dynamics (CFD) and the lumped-parameter thermal network (LPTN) [2,3,4,5].FEM and CFD both belong to the numerical method that can build meshed models of complex systems conveniently, and calculate the temperature distribution accurately [6,7,8]
Mellor et al first introduced the LPTN for electrical machines of totally enclosed fan cooled (TEFC) design
It is reasonable and scientific to validate the improved LPTN by the FEM model within the heat source
Summary
Thermal analysis is extremely important for the electrical machine design, because overheating will accelerate insulation aging, demagnetize permanent magnets, and even cause system failure [1]. In [20], Gerling et al made some improvements to the traditional LPTN They proposed the equivalent heat flux by halving the heating power to avoid the excessively large heat flux in heat source, so as to achieve the temperature drop balance. A novel improved LPTN based on the half-resistance theory and localization of heat generator is proposed to determine the maximum temperature in the uniform heat source.
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