Induction Motor Outputs FFT Analysis !

dear friends,

i got a problem that cant figure it out : during simulation of an induction motor, i want to analyze the output signal (that can be stator currents or rotor ones, torque, ....) using FFT simulink block. but the problem is FFT block only accepts "sample-based" input; while i guess my output from induction motor (wm) is time (frame) based and continuous! it says it only accepts "discrete" inputs as well. i really cant do anything to solve this thing!

i d be happy if someone has any ideas?

thanks, Amir