A system and method are disclosed for determining the mechanical angular position of a rotating member of a prime mover which is connected, directly, or indirectly, to an electric machine, such as a permanent magnet synchronous machine or an induction machine. The electrical angular position of the rotor of the electric machine is determined by a sensorless AC motor control system, such as a Field Oriented Control System or back EMF control system, and is used in turn to determine the mechanical angular position of the rotating member.