The Research About The Influence Of Special Magnetic Pole Shift Structure On The Operation Safety Of Bulb Tubular Turbine Generator

As a typical horizontal hydrogenerator,the bulb tubular unit is not only faced with the deterioration of the quality of the no-load voltage waveform,but also frequently appeared the phenomenon of overheated fuses of the damping bars during the operation of the unit due to its low speed,small air gap,few slots per pole and limited shape of the bulb.At present,however,the studies on the waveform distortion of no-load voltage and the damping winding loss and heating are mainly focused on the slot ratio and stator chute,while the studies on the special magnetic pole structure are rare.In view of this,the influence of special magnetic pole structure on the mass of no-load voltage waveform and the dissipation and heating of damping winding is studied in this paper.Firstly,SFWG34-44/6020（q=2）integer slot unit and SFWG36-72/7360（q=11/₂）fractional slot unit,which are representative among bulb tubular units,were selected as research objects.Based on the theory of rotating electromagnetic field and circuit,and in combination with the boundary value conditions,a quasi-three-dimensional layered nonlinear electromagnetic field-circuit coupling model was established,and the correctness of the model was verified.On this basis,a three-dimensional steady-state temperature field model of the magnetic pole system is established by selecting a magnetic pole as the heat source and taking its characteristics of heat dissipation and ventilation into full consideration.Secondly,the above model is used to calculate the deviation of 118 kinds of rotor inclined pole and pole shoe components and their matching structure schemes,which fully reveals the influence of the special magnetic pole deviation structure on the waveform distortion rate and damping winding loss and heating,discusses the optimization measures,and draws some useful conclusions.The conclusions are as follows:1)for fractional slot units and integer slot units,the rotor skew structure can not only optimize its no-load voltage waveform.However,the damping winding loss of two units cannot be suppressed to prevent the damping winding from overheating.From the calculation results of a large number of electromagnetic fields under the inclined pole structure of the fractional slot unit,it can be seen that the waveform quality optimization effect is the best at the inclined 1 pole.However,considering the effect of the inclined 0.5 pole optimization,the manufacturing process is simpler and the cost is more economical,so the inclined 0.5 pole scheme can be adopted in the actual production.Based on the calculation results of a large number of electromagnetic fields under the inclined pole structure of the integer slot unit,and considering the quality parameters of various waveforms,it is found that the skew level 1 optimization has the best effect,which is the best scheme.2)for fractional slot units,the offset structure of pole boot component will not only deteriorate the waveform quality of fractional slot units,but also aggravate the loss and heating of damping windings.For integer slot units,this structure plays a better role in optimizing the waveform quality.Compared with the optimization effect of the rotor inclined pole structure,the manufacturing process is simpler.Under the same circumstances,priority may be given to such programmes.From a large number of calculations,0.22t1 is the optimal scheme,at which time the quality parameters are optimal.At the same time,we find that this kind of scheme has no effect on damping winding loss.3)pole shoe component migration and rotor skew matching structure can optimize the no-load voltage waveform quality of the integer slot unit,which is better than the single rotor skew or pole shoe migration scheme.At the same time,it will also increase the loss and heat of the damping windings,and its deterioration capacity is stronger than that of the skew structure.These conclusions can provide a comprehensive engineering design reference for ensuring power quality optimization and safe and stable operation of the unit.As a typical horizontal hydro-generator,the bulb tubular unit is difficult to meet the requirements of electromagnetic design by amplifying stator diameter like the vertical turbine because of its low speed,small air gap,small number of slots per pole and phase.So on the electromagnetic design,especially prominent contradictions and difficulties,especially the determination of the stator slot number,often face per pole per phase slot number less than 2,the resulting harmonic component is bigger,resulting in no-load voltage waveform distortion,and the waveform distortion will not only increase the heat dissipation of the unit,it can also cause the protection misoperation of device,seriously affecting the safe and stable operation of the unit.At the same time,due to the small space and air gap of such units,and the ratio of core length to pole distance is generally greater than 4,it is more difficult to ventilate and dissipate heat.The above problems lead to not only the deterioration of the quality of no-load voltage waveform,but also the phenomenon of overheat fusing of damping strip.In view of this,this paper adopts the comprehensive analysis method of temperature field and electromagnetic field,and probes into the no-load voltage waveform and damping winding loss and heating problem in the light of the deviation of rotor inclined-pole and pole-boot components and the combination structure of the two,so as to provide more effective engineering design reference for the optimization of power quality and the safe and stable operation of the unit.