Depending on the quality of performance required for a particular application, such as for a low performance, the phase current and speed signals may be dispensed within the control system. The feedback signals are usually measured with transducers, which increase the cost of the electronic controller and its packaging size. In the case of a rotor position/speed transducer, the size of the motor housing and the cost are increased significantly. Emerging high-volume applications in heating, ventilation, and air conditioning (HVAC); fa pum home appliances; automobile accessory drives; and many others are cost sensitive. The performance requirements for such applications are not high as is required for machine tool servo drives. The requirement of low cost with high performance for motor drives has placed the agenda of low-cost, sensor-based or sensorless technology at the forefront of presentday research and development of motor drives. SRM drives are no exception to this trend, as seen from the high degree of interest shown by industrial and academic researchers worldwide on this topic. Rotor position can be directly measured by a rotor position sensor. However, mounting the rotor position sensor increases the size and cost of the overall system. The rotor position sensor is also a source of unreliability in applications of a harsh environment like in aircrafts, where a very high speed is required. It is also a source of unreliability at high temperatures and where electromagnetic interference presents. This is added to possibilities of mechanical failure. So, attention has been paid to indirect rotor position estimation to remove the rotor position sensor. Several indirect position sensing methods have been patented and published for sensorless control of SRM drives. For all previous techniques, it can not be claimed that one particular method is suitable for all types of applications. The position sensing techniques depend on a number of factors, such as, the type of application, the type of converter used and the control strategy. In this thesis we represent a sensorless method in switched reluctance motors based on incremental inductance computation to rotor position determination. The relationship between inductance and rotor position for each excitation current is unique over half a rotor pole pitch regardless of the rotor speed. This particular feature of an SRM is then used to find the rotor position from the estimated or measured inductance of a machine phase winding from the stored information of inductance vs. rotor position for each current in the control circuit. The burden of storing the inductance vs. rotor position information for all currents could be simplified in many ways a Keywords: Position Sensor, Switched Reluctance Motor, Incremental Inductance, Rotor Position.
