Most ac generators used in Power Stations are of the " Flux Cutting " types. Their effiencies range from less than 33% to slightly more than 60%. In their efficiency equations, they tend to stress on Power Factor correction. They tend to neglect the effect of " Lorentz Force " , F = BILN , which can be very huge, acting in the OPPOSITE direction to the rotation of the rotor. They have to use steam-turbines to overcome this force. My question is : Why " Lorentz Force " term not included in the Efficiency equations. If " Lorentz Force " is very difficult to solve, why not use " Magnetic Induction " type ac generators in Power Stations. Best Regards, UNGKU KAMAL.