Problems Calculating the Mechanical Starting Time

Please define the other symbols.

Sure! :)

J = moment of inertia of the rotor (kg*m^2)

P = active power (W)

H = Inertia time constant (seconds)

Ta= mechanical starting time or acceleration time constant (seconds)

w0 = rated mechanical speed (rad/sec.)

Thank you! :)

Any first-order system achieves >99% of the response to any change in 5 time-constants.

Sorry PWSlack, I dont understand your point. :S

Why is it important for calculating the value Ta?

Ta is arbitrary.

<...point...> ?

http://web.mit.edu/2.151/www/Handouts/FirstSecondOrder.pdf

Jorge, Perhaps you can explain how you intend to calculate the starting time if you don't have the most important variable, Wind Speed. For example if WS=0 then the time to start is ∞, if the wind speed is 30 m/s it will take less time than if it's 15 m/s, but I don't see that you provided any relationship between WS and power in your equation.

You're trying to use the standard equation for accelerating a rotating mass, but you're lacking the key variable, the net accelerating torque. Hint...google on the last two words. Think about it, the time to accelerate for a 2m blade is a lot different if it's 10m, more work on your model is required.

Hello, thank you very much for your answers! :)

RAmConsult, I am modelling the generator with one software, but it doesnt ask me for anything related to the wind. Its one synchronous generator which I can use it for many applications, for example, to supply power to one vessel. So, when modelling I dont need such information.

The program is using the inertia time constant related to nominal mechanical speed and nominal power. My doubt comes up when I compare my value with the one provided by the manufacturer... But maybe I shouldnt care too much about such difference.

Maybe the manufacturer is calculating it by using the values in the acceleration torque?

Thank you for your help and patient... still have too much to learn :)

Jorge, You are trying to model a system therefore you have to choose models consistent with the design of your system, using a bunch of generic modules that can't be customized or are irrelevant won't do much.

That's like using the model for a "wheel" without regard for its intended use, a bicycle wheel won't be a really good model for a motorcycle wheel even they may both have spokes and the same diameter.

It's time to start Googling for models of the performance of wind generators, there's lots of info out there which you, as a researcher/engineer/scientist, have to discover, analyze and choose as the best for your purposes. Class dismissed.

I'm failing to see how you can calculate mechanical starting time without knowing the applied torque, which in this case relates to wind speed as RAMConsultant said.

Or is that software IMPLYing torque from the kW? If so, seems to me that is putting the cart before the horse.

Thank everybody for your help!

I think I have understood you!

Have a nice day!