Rotor loss and temperature variation under single and combined faults composed of static air‐gap eccentricity and rotor inter‐turn short circuit in synchronous generators

Abstract

Abstract In this study, the rotor loss as well as the temperature variations due to the static air‐gap eccentricity (SAGE) and the rotor inter‐turn short circuit (RISC) in synchronous generators is presented. Different from the previous studies, this study investigates the loss/temperature changes under not only the single SAGE fault and the single RISC fault but also the combined faults (CF) that are composed of these two single faults. Detailed formula derivation on the hysteresis loss (HL) and the eddy current loss (ECL), together with the rotor temperature rise due to varied fault types and different operating conditions, are first carried out based on a theoretical analysis of the magnetic flux density (MFD) variation. Then, 3‐D finite element analysis (FEA) and experimental verifications are performed on a CS‐5 prototype generator that has two poles and a rated rotating speed of 3000 rpm. It shows that the occurrence of either SAGE or RISC will increase the rotor loss and temperature. Comparatively, the single RISC fault overweighs the single SAGE fault in the rotor temperature increment, while the combined fault overweighs both of these single faults. In the same fault cases, the rotor temperature will have the highest value under full‐load operation.

Keywords

• finite element analysis
• magnetic flux
• eddy current losses
• air gaps
• rotors
• poles and towers