Abstract: Several improvements are invented upon a known and well tested selfstarting vertical-axis wind turbine, for economically competitive power production by driving large grid-connected AC generators. It comprises: variable blade pitch-angle from 0 to 60 degrees, following variable wind speed for maximum efficiency and to keep constant turbine speed, variable blade camber limited to optimal lift-to-drag ratio, controled by pitch and cyclical variation of incidence-angle; improved airfoil shape of cambered blades; low cost automatic gear-train for two constant turbine speeds; protection against overload and prevention of power surge during wind gusts; low stress three-legged high tower assembled with nacelle and tail structure on ground level and erected by assembling segments of third leg one section at a time, and reducing costs of concrete footing, tower structure and, hoisting and assembling at ground level, enables a tower to be built to any height required to harness maximum wind energy.