Rotor and Nacelle Mass moment of Inertia Tensors

Dear Dr. jason Jonkman

I am trying to determine the inertia tensors of rotor and nacelle separately. I was able to find the combine (RNA) inertia values (Ixx, Iyy, Izz, Ixy, Izx, Iyz) of the 5MW wind turbine on this forum. However, i could not find separately the inertia values of rotor and nacelle. I will highly appreciate if you can guide me on the calculation procedure of these values separately or if you can provide me some values.

Link for combine RNA values: http://forums.nrel.gov/t/tower-eigenfrequencies-of-nrel-5mw-turbine/517/1

Best
Zahid

Dear Zahid,

The nacelle mass, center of mass, and inertia about the yaw axis are specified in the NREL 5-MW specifications report: nrel.gov/docs/fy09osti/38060.pdf. The other nacelle inertia terms were neglected. So, the rest of the rotor-nacelle assembly (RNA) inertia comes from the rotor.

Best regards,

Dear Dr. Jason Jonkman

Thank you for your kind response. Following your suggestion i calculated the Rotor inertia about its Center of Mass (Cm) using parallel axis theorem. I have briefly described the procedure of determination in the following steps.

Step 1: Transfer the nacelle inertia from yaw-axis to its Center of mass.
Step 2: Transfer the nacelle inertia from its center of mass to RNA center of mass.
Step 3: Subtract the nacelle inertia form RNA inertia (about RNA center of mass, obtained from another post on this forum) and thus found the Rotor inertia about RNA center of mass.
Step 4: Transfer Rotor inertia from RNA center of mass to Rotor center of mass

I have done this step wise calculation in an excel sheet and attached here. Can you please kindly give a look to the final values of Rotor inertia about Rotor center of mass if they seems correct.
5MW_Turbine_Inertia_2019.xlsx (206 KB)

Dear Zahid,

You’re overall approach is correct, but I found several mistakes in your spreadsheet. Please find my commented spreadsheet attached. With my corrections, I calculate the rotor mass and inertia about its CM as follows:
Mass = 110000
Ixx = 4.37E7
Iyy = 1.99E7
Izz = 2.01E7
Ixy = 0
Izx = 8.3E5
Iyz = 0

5MW_Turbine_Inertia_2019_JJ.xlsx (210 KB)
Best regards,

Dear Dr. Jason Jonkman

I followed all the comments and made the corrections and thus obtained the corrected values as you calculated. I am highly grateful for your valuable comments and corrections. Heartfelt thanks.

Zahid Ullah