You have two problems here. First, Mathf.Sin() takes radians, not degrees. Second is your use of while(). You want do a bit of work each frame, not do multiple moves per frame. Try this:
#pragma strict
var incr : float = 0.1;
var angle : float = 0.0;
function FixedUpdate () {
if (angle < 6.28){
transform.position = Vector3(30*Mathf.Sin(angle)*Time.deltaTime, 30*Mathf.Cos(angle)*Time.deltaTime,0);
angle+=0.1;
}
}