How do I model a spring in Ansys 2D for a linear generator?

[Jayaram12391]

Hi friends,

I am working on a model of linear generator. I have modeled the linear generator in Ansys 2D. Now I want to attach a spring to one end of the rotor and see how it works with the spring attached to it. How do I model the spring?

Also is there any proper way to determine the damping co-efficient of the system

Any help or suggestions will be highly appreciated. Thanks

 

[Hesch]

How do I model the spring?

First of all you have to determine what the input/output is to be in the model. Say that the input is some force, F, that affects the rotor, and that x is the position of the rotor, you will get a model like this:

m = mass of rotor
a(s) = acceleration
v(s) = velocity
x(s) = position
K = spring coefficient

Using Masons rule, you will get a transfer function: x(s)/F(s) = 1 / ( m*s² + K ) = ( 1/m) / ( s² + K/m ).

which can be rewritten

x(s)/F(s) = ( 1/m ) / ( s² + 2ζω_ns + ω_n² )

Here the damping ratio, ζ = 0 , because the coefficient to s = 0. So in this model no damping takes places, but that's because there is no friction and no power loss due to the generator included in this model.

is there any proper way to determine the damping co-efficient of the system

So to calculate a realistic damping coefficient, ζ > 0, you must introduce friction/power loss in the model.

 

[Jayaram12391]

Thank you very much for your answer. I know the stiffness of the spring to be attached to be 750pounds/inch. But i am not sure how I can introduce it into the ansys model.

Thanks for your explanation on damping co-efficient. I know the efficiency of the generator. I will try to calculate the damping co-efficient of the system.