High head pump-turbines

When the trigonometric function of the phase lag of the hydraulic excitation of the runner vanes, which varies in accordance with the combination of the number of runner vanes and the number of guide vanes of a high head pump/turbine, is denoted by cos((theta)Rn), the thickness of the crown along a circle of a diameter at a mid point of the diameter of the outermost periphery of the runner is denoted by tMC, the thickness of the band is denoted by tMB, the mean thickness of the crown at the outer peripheral portion of the runner is denoted by tC, the mean thickness of the band is denoted by tB, and the rigidity ratio of the crown and band to the runner vane is denoted by KR taking the rigidity of the runner vane as a reference, the moment coefficient CMO which is a function of cos((theta)RN) and the rigidity ratio KR is selected to be less than 0.5 in accordance with the value of cos((theta)Rn), and relations tC/tMC