About calculation of parameters of two-mass thermodynamic model of induction motor

The article substantiates a practical need for simple two-mass thermodynamic models of induction drive motors at evaluation of thermal state of the stator windings and their application at the thermal protection devices. It provides the mathematical description of the thermodynamic model in which the stator winding is designed as a separate (the first) assembly, whilst the other motor portion is the second one. Based on this description, the system of equations that establishes the relationship between parameters of a two-mass thermodynamic model was formed. The performed analysis of this equation system established relationship between its parameters. For the totally enclosed induction motors, the ratio of the average value of steady-state temperature rise of the second assembly to that of the stator winding ranges within 0.75 to 0.85 under nominal operation conditions. This analysis enabled solving the problem of obtaining simple analytical relations to calculate the thermal conductivities of a two-mass thermodynamic model of the totally enclosed induction motors with minimum data on internal motor parameters.