Use of infrared thermography for computation of heating curves and preliminary failure detection in induction motors

This paper proposes a methodology for the computation of the energy balance and heating curves of an induction motor taking as a basis the information provided by the application of the infrared thermography. Moreover, use of infrared thermography data to diagnose rotor bar failures is preliminarily studied. In the paper, a 1.1 kW induction motor is tested. Thermography images of the chassis temperature are captured at each second during the whole startup transient, from standstill till steady-state, by using an infrared camera connected to a laptop computer fitted with an acquisition and analysis program. A model based on the calculation of the heat losses by convection and radiation through the frame of the machine is developed. It uses the geometrical dimensions as well as temperature values obtained from the thermography images. The developed model enables studying any motor configuration and operating conditions by just varying thermal and geometry parameters. Finally, a preliminary study relying on the possible use of Thermography data for diagnosis of rotor failures is carried out. Experimental data corresponding to a healthy machine and a machine with broken bars are analysed and compared. This methodology will be the baseline for further complex failure diagnosis in electric motors.