Abstract:

                             This Research work represent an improved direct back EMF detection method .It is desirable in any kind of machine to use a method which is less dependable on the sensors and complex circuits, so in this paper a sensor less method is used to commutate and trigger the inverter connected to BLDC motor. A low pass filter arrangement with comparator is used for detection of back EMF with hall effect sensors. Hall effect signals gives the information of the operations in the BLDC motor in this work hall effect signals are used for the gate pulses for the inverter. In this research work rotor position is determined by the Zero Crossing Detection (ZCD) of back EMF. Unlike old methods of calculating Back EMF of the BLDC by creating a virtual neutral point, a complimentary method is used. This method provides a wide range of speed. A simple approach of detecting back EMF using comparator and RC filter is defined. This method provides an improved version of the back EMF. It is shown that BLDC motor is a good choice in automotive industry due to higher efficiency, higher power density and higher speed ranges compare to other motor types. BLDC motor model with improved back EMF and rotor position detection method is presented in this research work with stator current, Back EMF and rotor speed. The proposed model is simulated in MATLAB / SIMULINK. Output characteristics and simplicity of model make it effectively useful in design of BLDC motor drives with different control algorithms in different applications.

Keywords: -BLDC (Brushless DC Motor), RC filter, back EMF