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Li Z.,Lanzhou University of Technology | Yang F.,Lanzhou University of Technology | Pu X.,Gansu Chaijiaxia Hydropower Station | Chen J.,Lanzhou University of Technology | Si G.,Lanzhou University of Technology
Applied Mechanics and Materials | Year: 2012

The rotor vibration of the unit is sensitive to the running conditions for the turbine group low head, high flow characteristics. It easily lead the rotor bracket of oblique arm structure to crack. The reason of rotor bracket cracks is proved by ANSYS analysis and its repair program have been identified. Running for some time after repair, the main parameters, such as air-gap and other unit operation, have been analyzed. The results are satisfactory, which verifies that the analysis of the rotor bracket crack repair is objective and reasonable. © (2012) Trans Tech Publications, Switzerland. Source


Li Z.,Lanzhou University of Technology | Yang F.,Lanzhou University of Technology | Si G.,Research and Development Center | Wang D.,Gansu Chaijiaxia Hydropower Station
Sensors and Transducers | Year: 2013

The generator vibration of the unit is sensitive to the running conditions for the low-head turbine group's low head, high flow characteristics. The generator local stress concentration often leads to fatigue rupture of the metal structure, which will also affect its reliability. It easily leads the generator bracket of oblique arm structure to cracking and rupture. The reason of the cracking and rupture is proved by numerical analysis and its repair plan has been identified. On-site repair process should be strictly controlled, to ensure the greatest degree of welding quality and the elimination of welding stresses. Running for some time after repair, the main parameters, such as air-gap and other unit operation, have been analyzed. The results are satisfying, and confirm that the analysis of the generator bracket crack repair is objective and reasonable. © 2013 IFSA. Source


Li Z.,Lanzhou University of Technology | Yang F.,Lanzhou University of Technology | Shi S.,Gansu Chaijiaxia Hydropower Station | Wang D.,Gansu Chaijiaxia Hydropower Station | Li X.,Qingdao University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2013

Intensified rotor vibrations of a generating unit under the variation of hydraulic condition of low head turbine can easily cause cracking of the rotor bracket of oblique arm structure. Numerical calculation of the on-site unit operation in this study indicates the possibility and safety of unit running for a certain period after the rotor bracket was cracked, and an analysis of air gap for such generator verifies the stability of its operation and the numerical results of the cracked rotor bracket. This work would provide a basis for time scheduling of rotor maintenance and repair to improve economic benefits of power generation in flood season. © right. Source


Li Z.,Lanzhou University of Technology | Yang F.,Lanzhou University of Technology | Wang D.,Gansu Chaijiaxia Hydropower Station | Deng Y.,Lanzhou University of Technology | Ma B.,Lanzhou University of Technology
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Low-head hydro-generators are an internationally recognized renewable green clean energy with the most advantages in China. At present, hydro-generators operating in the countryside with electrified wire netting are generally a horizontal structure with a low-head and small capacity. With the increase of low head hydroelectric generating turbines operating in the river, there still exist different problems in the various links. However, a relatively short history of the design, manufacture, installation, operation and maintenance of low head hydraulic turbines may easily lead to the increase of roundness deformation of the generator in operation. Field technicians usually do nothing more that an analysis of the structure and operating conditions. Moreover, the research by experts and scholars the problems are limited. The generator related accidents are more common both at home and abroad, and have become more and more serious. This paper studied this problem on the practical side. The existence of gravity and centrifugal force during operation creates eccentricity and an uneven air gap in the low head hydraulic generator, forming an unbalanced magnetic field which leads to an unbalanced magnetic pull. The effect of the alternating load finally not only creates an increase of the roundness deformation of the generator stator and the rotor, but also creates a torsional bending of the generator, increasing vibrations and possibly a generator fatal "friction" accident. This paper took unit # 1 at the Chaijiaxia hydropower station on the Yellow River as the research object through the parameter analysis of the generator eccentricity and the air gap, the exciting current in steady and transient states and the loss of excitation in generator, and the generator temperature, including the change law of unbalanced electromagnetic force, axis changes, torsional bending, vibrations, and the roundness deformation. On this basis, by studying the generator magnetic force, torque, analytical equations of coupled bending, and torsional vibrations of the rotor, this paper described, the cause of the change of the generator roundness deformation through the qualitative analysis of the gas gap, unbalanced magnetic pull, as well as the generator operation stability under the condition of static eccentricity, eccentric motion and eccentric vibrations. It undertook a quantitative analysis of the variation of the generator air-gap and magnetic pull that influenced the roundness deformation, and the cause that produced vibration, overheating, and fatigue in the load condition via finite element calculation. According to this research conclusion, running measures have been put forward to make the generator run in its optimal condition, and the obvious effect has been obtained. Moreover, the theoretical basis, the analysis methods, and operation mode are provided to solve the problem of the roundness deformation in a low head hydraulic generator. Source

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