A nonlinear model and viscosity solution for the temperature field of an oil-immersed self-cooled three-phrase transformer

In this paper, on the basis of the characteristics of an oil-immersed self-cooled three-phrase transformer, we establish a mathematical model of the three-dimensional temperature field. But because the specific heat, density, heat sources and coefficient of heat transfer are discontinuous and non-differentiable, the problem has no analytical solution. We decompose the problem into seven subproblems, and prove the existence and uniqueness of a viscosity solution for every subproblem, by combining Perron’s method with the technique of coupled solutions.