Abstract – This paper presents a position sensorless operation of BLDC motor. Commutation is based on detection of back-EMF zero crossing from the terminal voltages. The method make use of the difference of line voltages measured at the terminals of the motor. The difference of line voltages provide an amplified version of back EMF. The commutation signals are obtained without the motor neutral voltage. The dc supply to the inverter is supplied by a three level boost type converter with power factor correction. Capacitor voltage balancing is also achieved. The effectiveness of the proposed method is demonstrated through simulation results. The simulation result shows that the output voltage of converter remains regulated, the capacitor voltages are balanced. Also the power factor obtained is nearly unity.

Abstract— Torque ripple is one of the major disadvantages of Switched Reluctance Motor (SRM) drives due to its double salient geometry and it is a serious drawback in applications that require smooth torque and high dynamic performances. This paper presents the minimization of torque ripple in SRM using an enhanced direct instantaneous torque control. Linear and non linear modelling is done in SIMULINK. SRM is modelled in ANSYS MAXWELL (FEA method) and the inductance and torque values are obtained. These values have been provided as look up table in MATLAB for obtaining the non linear characteristics of SRM. The switching control rules in each inductance region are then described according to the characteristics of asymmetric power converter. In order to test the method, a SRM drive system is simulated in MATLAB SIMULINK after detailed analysis of linear and non linear models.