The Simple free-body diagram of the drivetrain equation

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Sina.Ameli
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Location: Florida

The Simple free-body diagram of the drivetrain equation

Postby Sina.Ameli » Thu Jan 24, 2019 8:42 am

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 (https://www.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:

Capture.PNG
Capture.PNG (6.24 KiB) Viewed 1904 times


The other equation I saw is as follows:
Capture2.PNG
Capture2.PNG (6.36 KiB) Viewed 1904 times


Why are they different in only "Ngear"?

Thanks,
Best Regards,
Sina

Jason.Jonkman
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Location: Boulder, CO
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Re: The Simple free-body diagram of the drivetrain equation

Postby Jason.Jonkman » Thu Jan 24, 2019 3:35 pm

Dear Sina,

In Eq. (7-5), the generator torque is expressed relative to the high-speed shaft side of the drivetrain. In the other equation, the generator torque is expressed relative to the low-speed shaft. (The low-speed shaft torque is larger than the high-speed shaft torque by a factor of the gearbox ratio.)

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


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