Dear Dr. Jonkman,

I realized a difference between the equation (7-5) of the motion of the drivetrain in your 5-MW offshore wind turbine document (nrel.gov/docs/fy09osti/38060.pdf) and other books and journal papers.

The difference is that other books eliminated “Ngear” that is multiplied by generator torque in your document.

Your equation:

The other equation I saw is as follows:

Why are they different in only “Ngear”?

Thanks,

Best Regards,

Sina