Chapter 11 - Single-phase controlled rectifiers

Abstract

This chapter focuses on single-phase controlled rectifiers, which are used in a wide range of applications. Single-phase rectifiers can be classified into two big categories: topologies working with low switching frequency, also known as line commutated or phase controlled rectifiers and Circuits working with high switching frequency, also known as power factor correctors (PFCs). Line-commutated rectifiers with diodes do not allow the control of power being converted from ac to dc. This control can be achieved with the use of thyristors. High power factor rectifiers can be classified in regenerative and non-regenerative topologies. The single-phase half-wave rectifier uses a single thyristor to control the load voltage. The control of the load voltage is performed by delaying the firing pulse by an angle α. Important application areas of controlled rectifiers include uninterruptible power supplies (UPS), for feeding critical loads. A fully controlled or half-controlled rectifier is used to generate the dc voltage for the inverter. In addition, the input rectifier acts as a battery charger. The main disadvantages of the classical line-commutated rectifiers are that they produce a lagging displacement factor with respect to the voltage of the utility; and they generate an important amount of input current harmonics.