Ripple Control in AC to DC Converter

Abstract

When a sinusoidal voltage is converted into dc, the output voltage waveform inherently contains ripples. Ripple is an unwanted ac component in dc output. Smaller value of ripple factor is desirable. Ideal value of ripple factor is zero. Zero ripple factor means a perfectly dc quantity. Undesirable effects of the ripple include equipment heating, increased losses, and reduced equipment life among others. Ripple factor of a single-phase half-wave uncontrolled rectifier is 1.21. This value is unacceptably high. To overcome the problem, a single-phase full-wave uncontrolled rectifier is proposed with a ripple factor of 0.48. In this paper, the ripple factor for above mentioned rectifiers with a resistive load is presented mathematically and pictorially. The rectifiers are modeled and waveforms are obtained using a computer program called Alternative Transients program, ATP. At the end, results are presented and compared. Ripple factor was improved by a factor of 40% by using a 2-pulse rectifier instead of a 1-pulse rectifier. Theoretically, if the number of pulses is increased to infinity, the ripple factor will reduce to zero giving a perfect dc output. Subsequently, 6-pulse, 12-pulse, and 18-pulse rectifiers will be modeled and advanced studies will be carried out. This paper will help understand the one of the power quality components called ripple in dc output. The paper will be useful for college seniors, graduated students, and power electronics design engineers.