## Mass moment of inertia of the rotor

Discuss the theory and modeling of rotor aerodynamics.

Moderator: Bonnie.Jonkman

Posts: 9
Joined: Wed Dec 09, 2015 8:50 am
Organization: Fraunhofer IWES
Location: Germany

### Mass moment of inertia of the rotor

Dear all,

for the control system design of a wind turbine, I need the second mass moment of inertia
of the rotor. Normally, I take this value from the summary file. However, this time the
summary file gives the following

Rotor mass properties:
Rotor Mass (kg) 839345.562
Rotor Inertia (kg-m^2)*************

Someone knows, why the inertia is not printed, maybe a format error or wrong
set up in the input file? Is it possible to transform the "*" in numbers? Can be the
information obtained in other way?

Many thanks in advance for any help.

Jason.Jonkman
Posts: 4962
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Mass moment of inertia of the rotor

It looks like the number of digits in the rotor inertia calculated by ElastoDyn is more than the format statement allows. This is likely because the mass of your rotor is quite large. What wind turbine are you modeling?

You can access the rotor inertia by changing the format statement and recompiling FAST. See ElastoDyn SUBROUTINE ElastoDyn.f90/ED_PrintSum().

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Posts: 9
Joined: Wed Dec 09, 2015 8:50 am
Organization: Fraunhofer IWES
Location: Germany

### Re: Mass moment of inertia of the rotor

Dear Jason,

thank you very much for your answer. Yes, after compiling the FASTlib with other format statement, the problem was solved.
The wind turbine is a 20 MW machine.
Best regards