Design and Construction of Induction Motor Thermal Monitoring System

Rotor and stator temperature rise in induction motors is considered to be a major cause of motor insulation degradation and motor failures. In most cases, it is necessary to monitor rotor bars and stator windings to make sure that their temperature remains below the allowable limits. In this paper, design and implementation of a temperature measuring system suitable for three-phase induction motors is described. The system contains two parts, rotating and stationary. In this work, digital temperature sensors are installed on rotor and stator windings. The data from the thermal sensors on the rotor is digitized using electronic parts and transmitted via light through IR receiver and transmitter between the rotor and the stator. A data acquisition system is employed for capturing data from electronic parts to PC for further analysis and monitoring purposes. Implementation of the monitoring system on a 5.5 kW 3-phase squirrel cage induction motor is described. Temperature rise in rotor bars and stator windings are monitored under no load and locked rotor conditions. It is shown that the system is capable for thermal monitoring of the test motor under various supply and load conditions