Study On No-load Voltage Waveform Optimization And Damping Bar Loss Suppression Of Large Bulb Tubular Hydrogenerator

As a renewable green resource,water resource has abundant potential for development and utilization.Nowadays,in the upstream areas where the water flow gap is large,the development of large hydro-power stations with high heads has been roughly completed,while in the midstream and downstream areas,the indicator for the establishment of low head hydro-power stations is still unfinished.Compared with the traditional axial flow unit,the tubular flow unit has the advantages of a more reasonable motor structure,lower investment cost of the hydro-power station and higher power generation efficiency,which makes it have an important position that cannot be replaced in large and medium-sized hydro-power stations with a low head of 3-20 meter.The unreasonable damping winding structure will not only cause the temperature of the damping bar to be too high or even break,but also make the no-load voltage waveform worse,ultimately reducing the power quality of the power grid.Therefore,it is very necessary to study the no-load voltage waveform,damping bar loss and heat together.This article aims to improve the quality of the no-load voltage waveform and reduce the probability of excessive temperature or even fracture of the damping bar.Now this article combines basic theoretical knowledge such as electromagnetic field,temperature field,and heat transfer,uses the three-dimensional nonlinear time-varying electromagnetic field-circuit coupling model and three-dimensional steady-state temperature field model,contrary to damping winding and stator slot,adopts the adjustment of slot pitch ratio,skew slot degree,number of damping bar and damping winding center-line,performs time-step finite element simulation calculations on them,then analyze the basic rules of regulation of these different motor structures on no-load voltage waveform and damper bar loss and temperature rise,the following is the main research work of this article:1 Based on the electromagnetic field and circuit theory,considering the characteristics of the time-varying,non-linear and continuous movement of the electromagnetic field of the tubular motor,a three-dimensional electromagnetic field model that matches these characteristics and combines stator winding and rotor winding circuits is established to obtain related parameters of damper bar loss and no-load voltage waveform.Subsequently,half of the magnetic poles of the motor rotor is selected as the solution area,and after fully considering the rotor thermal conductivity and ventilation characteristics,a three-dimensional steady-state temperature field simulation model is established to analyze the damping bar heat.2 Through the above simulation model,this paper uses the finite element simulation software to calculate the two representative q=11/2 fractional slot units and q = 2 integral slot unit,according to the obtained simulation data,adjusting all the above-mentioned structures can improve the quality of the no-load voltage waveform to a certain extent,of which the effect of changing the degree of stator skew is most significant;except that the combination of the center line offset of the damping bar and the stator skew slot has a poor heating effect on reducing the loss of the damping bar,the other structures can improve the heating to a certain extent..And on this basis,the measures that can simultaneously improve the quality of the no-load voltage waveform and suppress the heating of the damping bar are discussed.