In situ non-invasive identification of thermal resistances for small DC motor

This paper presents a new method for the identification of thermal resistances. We propose here a thermal model that allows users to get rotor temperature given current and case temperature as inputs. This identification process presents two advantages, compared with existing methods: it can be used onsite in real time and it is non-invasive. Two experiments are carried out. In the first one, the ambient temperature simulated in a heat chamber is changed drastically using the same motor current. In the second experiment, the ambient temperature is kept constant while varying motor current on a large scale. Thermal resistances obtained from experiments are compared with catalog data. Results shows that the internal thermal resistance is significantly different from the manufacturer value, and that the thermal resistance between stator and external world can be measured with better accuracy as motor housing is taken into account in the identification process.