The relationship between the electrical generator rpm, the number of generator poles n, and the current/voltage frequency f is given by Eqn. 6 in the book chapter as: f = (n * rpm) / 120 [Hz] What would be the number of generator poles needed in the USA and in Europe/Asia for: 1. An off-shelf generator with an rpm of 1800 connected to a wind turbine by a gearbox/transmission? 2. A gearless, direct drive wind turbine with a gearing ratio of unity and an rpm of 18