Investigation of thermal instability testing on synchronous generator rotors using an experimental direct mapping method

Abstract: Utilities employ Thermal instability testing (TIT) for final acceptance testing after the construction and refurbishment of turbogenerator rotors. This type of testing is performed through two methodologies namely current injection and friction/windage in order to assess the thermal sensitivity of the machine’s rotor. Although there are distinct differences between the two methods, no apparent preference is shown by service providers/OEMS globally. There is also no definitive evidence or standards that offer a comparison of the two methods and suitability assessment thereof. The presented research investigates these two methods of TIT for a synchronous generator rotor. An experimental setup with infrared thermography is employed to investigate the thermal behaviour of the machine’s rotor for each of the test methods. Experimental results show that the thermal behavior of the generator rotor is significantly different for each methodology. It is also shown in this paper that contemporary TIT practice requires an augmented test methodology

Investigation into high-speed thermal instability testing of synchronous turbo-generator rotors

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2017The research presented in this thesis conclusively shows that the most effective method to perform synchronous turbo-generator rotor Thermal Instability Testing is by utilising the current injection method of condition assessment. Analysis of the experiences of a local utility for well over a decade has uncovered a high number of rotors failing thermal instability testing in recent years. This trend has brought the current testing methodology into question. Two different assessment modes of testing have been found to be utilised internationally without preference, namely, current injection and friction/windage. By determining the method that is best suited to detect a thermally sensitive rotor a service provider can benefit by improved rotor reliability as well as cost saving. The evaluation is accomplished by utilising a scaled down experimental setup based on the model of a local testing facility as well as a 600 MW turbo-generator rotor. A direct thermal mapping technique has been devised utilising infrared thermography to capture the thermal distribution of the rotor surface under different test conditions. The results obtained have shown that the methods differ substantially with the friction method exhibiting a uniform surface distribution and the current-injection method exhibiting areas of higher temperature concentration around the rotor pole faces. However, weaknesses do exist in present-day testing techniques in the form of inaccurate temperature measurements during testing as well as little consideration given to external factors such as the interaction between the slip-ring and brush-gear that have the potential to influence test outcomes. A presented augmented method of performing thermal sensitivity testing taking advantage of infrared thermography is found to improve testing accuracy and aid in fault detection and location. Current thermal instability testing coupled with the direct thermal mapping method has been demonstrated to be the most effective means for performing rotor thermal sensitivity testing.MT201

Thermographical analysis of turbo-generator rotor

Abstract: Refurbished or newly constructed utility-scale turbo-generator rotors requires stringent acceptance testing before commissioning and subsequent operation thereof. Conventional methods of testing are inadequate in detecting and locating thermally induced problems. This paper presents a thermographic method for carrying out thermal instability testing of generator rotors. An experimental setup is used to map the thermal distribution of the generator rotor. Implementation and testing of the method is carried out in a laboratory setting using a down-scaled turbo-generator rotor

Thermal instability analysis of a synchronous generator rotor using direct mapping

Abstract: Abstract: This paper presents a direct and practical method for mapping the thermal behaviour of a synchronous generator. Since temperature variations can lead to rotor thermal instability which adversely affects the operation of the generating unit, a better understanding of this phenomenon is required. The two main methods of performing thermal instability testing - direct current injection and friction/windage - are found to be practiced internationally without preference. Infrared thermography is used here as a means of determining the thermal performance of the rotor under different testing scenarios. The experimental testing is conducted using a scaled setup of a balancing facility and a 600 MW generator rotor. The results obtained are presented in the form of surface temperature maps. The thermal distribution of the two different methods were found to differ substantially with the friction method exhibiting a uniform surface distribution while the current method exhibited areas of higher temperature concentration around the rotor pole faces

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

SIRM 2017

This volume contains selected papers presented at the 12th International Conference on vibrations in rotating machines, SIRM, which took place February 15-17, 2017 at the campus of the Graz University of Technology. By all meaningful measures, SIRM was a great success, attracting about 120 participants (ranging from senior colleagues to graduate students) from 14 countries. Latest trends in theoretical research, development, design and machine maintenance have been discussed between machine manufacturers, machine operators and scientific representatives in the field of rotor dynamics. SIRM 2017 included thematic sessions on the following topics: Rotordynamics, Stability, Friction, Monitoring, Electrical Machines, Torsional Vibrations, Blade Vibrations, Balancing, Parametric Excitation, and Bearings. The papers struck an admirable balance between theory, analysis, computation and experiment, thus contributing a richly diverse set of perspectives and methods to the audience of the conference

Bibliography of Lewis Research Center technical publications announced in 1980

This compilation of abstracts describes and indexes over 780 research reports, journal articles, conference presentations, patents and patent applications, and theses resulting from the scientific and engineering work performed and managed by the Lewis Research Center in 1980. All the publications were announced in Scientific and Technical Aerospace Reports and/or International Aerospace Abstracts

12th International Conference on Vibrations in Rotating Machinery

Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction

12th International Conference on Vibrations in Rotating Machinery

Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction