Determination of heat circumstances in the motor protection switch considering air flow

This paper presents the determination of heat conditions in the motor protection switch, with consideration to the air flow inside the switch. The finite-element method (FEM) was used for the calculation of the temperature conditions. Because of the temperature-dependent material properties and the geometrical peculiarities of the model, a sequential procedure for the calculation of the heat circumstances was developed. The specificity of the model is that the inside air is separated into two domains. These two domains are physically completely separated, but they have an indirect influence on each other through the thermal conductivity of partition walls