You only get into the "if" if n_motor_TASIT_1(i) is less than 750, but your while only executes if it's more than 750. Those are contradictory, so if it gets inside the "if" it will never execute the "while".
Plus your while loop never changes n_motor_TASIT_1(i) so even if it did get into the while loop, it would never get out of it. You have an infinite loop because you do not have a secondary fail-safe condition where you check the number of iterations and bail out if it's unreasonably large, and no way to ever change the single condition you are checking.