The paper describes a lumped parameter thermal model of an electric motor of TEFC design. The transient thermal characteristics of the motor is estimated from a lumped parameter thermal model. Experiments were performed on a 3.5 H.P. capacitor run single-phase induction motor and the simulated results were verified with experimental data. It was found that the software gave a satisfactory estimation of the thermal characteristics of the TEFC single-phase induction motor examined. The software uses all the motor dimensions as input data for the thermal model, so it is useful at the design stage for performance prediction of the designed machine. Though developed for a single-phase induction motor, the model is equally applicable for any motors of TEFC design.