Analysis of thermal instability test methodologies for synchronous generator rotors

Abstract: Thermal instability testing (TIT) is utilised by service providers as a final proving test during the construction, repair and overhaul of large turbo-generator rotors. This test is typically performed using two methodologies – i.e. current injection and friction/windage methods – to evaluate the thermal sensitivity of the generator rotor. Although these methods are distinctly different – service providers/OEMS worldwide show no preference towards a methodology and there is no substantiating evidence or international standards which provide insight into which method is most suitable. This paper investigates these two methods of TIT for synchronous generator rotors. A specialised experimental configuration utilising infrared thermography is used analyse the thermal behaviour a synchronous generator rotor under different test conditions. Experimental results indicate that there are substantial differences in the behaviour of the rotor under the two different methodologies and that an augmented test methodology is required to improve TIT