Calculation And Analysis On The Eddy Current Losses And The Circulating Current Losses For 1000MW Hydro-generator

There are considerable eddy current losses and circulating current losses in the hydro-generator, that the eddy current losses are existed in the rotor damper bars and the circulating current losses are existed in the stator strands mainly. In recent years, with the unit capacity of hydro-generator increasing, the issues caused by the eddy current losses and the circulating current losses become more and more prominent. The factors are further researched on the basis of the eddy current losses are calculated accurately, and the odd strand transposition is proposed to improve the stator strand transposition method. The circulating current losses are calculated, and the results are compared with the traditional strands transposition.Firstly, the electromagnetic field under rated load and asymmetrical operation is calculated by a 2-D electromagnetic field-circuit-moving coupling model. On this basis the eddy current losses in the damper bars of one magnetic pole under different operating conditions are calculated accurately. The eddy current losses in the damper bars under different operating conditions are also compared and analyzed.Secondly, the effects of connection mode of damper system, the radius of the damper bars and the material of damper bars on eddy current losses were discussed by only change one of them and keep the other parameters remained unchanged. The distribution of the eddy current losses of this case is compared with the eddy current losses of original design. Furthermore, the influencing factors on the eddy current losses in the damper bars is analyzed comprehensively. Finally, An improved stator bar transposition method which named odd strand transposition is proposed. The circulating current losses of traditional strands transposition and odd strand transposition under the four stator bar transposition methods were calculated accurately using leakage potential method, the results of differnet transposition methods is compared and analyzed.All these can benefit the theoretical analysis and the optimized design of the damper bar parameters and stator bar transposition method of 1000MW hydro-generator.