Heat analysis of thermal overload relays using 3-D finite element method

In designing a thermal overload relay, it is necessary to analyze the thermal characteristics of several trial models. Up to now, this has been done by measuring the temperatures on a number of positions in the trial models. This experimental method is undoubtedly expensive. In this paper, the temperature distribution of a thermal overload relay is obtained by using 3-D finite element analysis taking into account the current distribution in current-carrying conductors. It is shown that the authors' 3-D analysis is capable of evaluating a new design of thermal overload relays.