Minimization of Torque Ripple for a 4-ø BLDC Motor with Non-Ideal Back Emf by using Phase to Phase Back-Emf Estimation

Abstract— Brushless motors are gaining attention from various Industrial manufactures because of its high efficiency, noise less operation and high speeds. In conventional control methods of Brushless Dc motors, the back electromotive force is assumed to be in ideal form i.e., Trapezoidal form, so that rectangular currents are injected from the inverter. In real time, the back-Emf may not to be trapezoidal due to its magnetic materials, design considerations, limitations in manufacturing, etc., this makes the generation of ripples in torque waveform which is inacceptable in sensitive Industries. In this paper, the ripples generated in torque waveform due to non ideality of back-Emf is compensated by injecting the currents which are proportional to the instantaneous phase to phase back Emf magnitude for a four phase Bldc Motor.