Pitch accelerations

Wind & Water Structural Analysis
1

Hello,

I’m looking to study pitch dynamic effects on swept blades. Does anybody know of reasonable limits of pitch system accelerations?

Thanks,

2

Oh, we can get 150-200 degrees/second^2 on the CARTs, and those are really, really fast compared to most commercial systems which are usually less than half of that.

It’s pretty easy to figure out. Get yourself some specs on pitch motors including stall torque and inertia and assume all the inertia is in them. Then, calculate a pitch gear ratio from maximum motor RPM and maximum expected pitch rate (8-12 degrees per second) and you have it. The blade’s pitch inertia is almost zero. The gearbox adds some, but not a ton.

3

Thanks Lee Jay for the information on the CARTs and the method to determine rate from commercial hardware.

4

Scott,

For megawatt wind turbines, typical pitch rate is 6-8 deg/sec and pitch acceleration 30-40 deg/sec^2.

Khanh