Physical Field Analysis And Prevention Of Overheated Ablation Of The Surface Of A Bulb Tubular Turbine Generator

Compared with the traditional axial flow motor,the overall investment of the bulb tubular turbine generator is shorter,the construction period is shorter,the generator size is smaller,and the efficiency of the runner is also higher.And because of its use of low head and large flow hydraulic resources,its utilization rate is almost 100% in large and medium-sized hydropower stations in the water head section of 20 m and below in areas with small river drop in China.However,in recent years,bulb-type tubular units of several hydropower stations at home and abroad have successively developed a new type of fault in the surface of the rotor pole piece with a common law.Many manufacturers at home and abroad have polished,pickled and brushed ablated pole pieces,but still can not prevent such failures from happening again.It has brought serious economic losses to the unit design manufacturers and users.Therefore,it is necessary to study and establish electromagnetic field and temperature field analysis models for such faults.Combined with the relevant project site data,the failure mechanism is analyzed and revealed,which provides a more effective and reliable guidance basis for faulty generator reconstruction and generator optimization design.Firstly,in order to obtain the heat source and loss of the hydro-generator pole shoe region,based on the electromagnetic field theory and circuit theory,a three-dimensional layered-path coupling model of the hydro-generator is established.The no-load voltage waveform and the pole shoe region loss analysis model are further established.Based on the theory of heat transfer,the three-dimensional steady-state temperature field model of the rotor of the hydro-generator rotor is established by the thermal conduction and thermal convection analysis of the magnetic pole system.The correctness and rationality of the model are verified by simulation experiments,which laid the theoretical foundation.Secondly,on the basis of the above theoretical model,the influence of different structural parameters on the loss and heat of the pole piece components such as iron core and damper winding,and the quality of the no-load voltage waveform of the unit are analyzed by using the calculation software.Furthermore,it reasonably infers and reveals the causes of such faults,and provides practical and reliable theoretical support and reference for fault real machine transformation.Finally,based on the above research results,considering the influence of factors such as the no-load voltage waveform quality,the real machine transformation scheme is proposed.According to the scheme,the real machine reconstruction construction and the rotor pole shoe surface temperature measurement test are implemented.The test results show that the scheme effectively reduces the surface temperature of the magnetic pole and plays a very good role in suppressing the ablation fault of the magnetic pole shoe of the hydro-generator,which further proves that the research results in this paper are accurate and reasonable.