INVESTIGATIONS ON PWM CONVERTER FED DC DRIVE OPERATING IN REGENERATING MODE

Abstract

Statically controlled D.C. drives are widely used due to ease in control as variable speed drive in industry. Regenerative braking operation is used invariably in de motor drive employing separate excitation and where frequent stopping and speed reversal is required. Regenerative braking . is employed in dual converter fed dc motor drive. The inversion mode of converter is required for regenerative operation of DC drive. The input performance of phase controlled converter namely input power factor deteriorates at reduced output voltage. This problem is rectified in PWM converter, which makes the fundamental input power factor unity and also reduces the input AC current harmonics. This dissertation deals with the development and performance investigation of PWM converter fed dc drive operating in regenerating mode. The performance of the drive is investigated in both open and closed loop under steady state condition. The three phase PWM converter is realized using three MOSFETs in series with fast recovery diode and three thyristors. The closed loop current control for maintaining constant current is realized through software using 8031 single chip micro-controller dedicated system. First chapter discusses the dc machine speed control methods, disadvantages suffered by phase controlled converter and various power factor improvement techniques. Second chapter deals with literature review related to the proposed scheme. Chapter three discussed in detail about the PWM converter and PWM techniques. Fourth chapter describe the hardware required for the proposed scheme and its software implementation. Chapter five gives the experimental results and last chapter draws the conclusion and scope for future work.