Investigations on current control and speed control of VSI CSI fed permanent magnet brushless dc motor

Abstract

Permanent magnet Brushless DC motor drives are being employed in newlinemany variable speed applications due to their high efficiency, silent operation, newlinecompact size, high reliability, ease of control and low maintenance newlinerequirements. The main aim of this research is to reduce the switching losses, newlinevalue of Inductance, Current ripples, cost and also to improve the dynamic newlineperformance of the BLDC motor drive system. These goals have been met by newlineusing Current control methodology, Resonant DC link voltage method, Power newlinefactor correction converter, careful component design of a converter in the newlineBLDC motor drive system. In this research there are four main objectives, the first being is to build newlinea simple current controlled modulation technique for Brushless DC motor newlineusing common DC signal. This current controlled technique is based on the newlinegeneration of quasi- square wave currents using only one controller for the newlinethree phases. The equivalent DC current is obtained through the sensing of the newlinearmature currents of a BLDC motor. These currents are rectified and DC newlinecomponent is then used to drive the BLDC motor. The advantages of this newlinetechnique are: (a) The DC link current measurement is not required (b) Phase newlineover currents are eliminated, then by controlling the torque and speed can be adjusted for a wide range. The second main task is to reduce the high device newlinevoltage stress and large DC link voltage ripples in the BLDC motor drive newlinesystem. This work presents a transformer based Resonant DC link inverter for newlinebrushless DC motor. DC link voltage notches during chopping switches newlinecommutation for all the switches working in zero voltage switching condition. newlineAs the switching frequency is high in this inverter, the switching acoustic newlinenoise can be eliminated. Only one DC link voltage notch is needed during one newlinePWM cycle and the switching frequency of the auxiliary switches would not newlinehigher than the PWM frequency.