From The Switching Function: Analysis of Power Electronic Circuits

6.1 Introduction

Two cases are examined here: resistive load and inductive load. In the latter case continuous and discontinuous conduction, with and without a free-wheeling diode are considered. Triggering of the thyristor is effected by supplying a positive train of pulses to their gates. Only one thyristor is conducting at a time and it remains conducting until the voltage across it is reversed or the current through it becomes zero. The effect of overlap for the three-phase half-wave phase controlled converter is not examined. Overlap is examined in the next chapter for the full wave system. Its findings can easily be adopted for the half-wave converter.

The delay-firing angle ? for the red phase is measured in the usual way from the point of the first crossing of the blue and red phases; hence a fixed delay of 30 always exists for ? with reference to the red line. The delay angle for the other two phases is measured in a similar way. The switching function of these circuits is a single pulse, which is repeated for every mains cycle. There are three switching functions, one for each phase, displaced by 120 .

6.2 Mathematical Modelling of the Three-phase Half-wave Phase Controlled Converter

The circuit diagram of a half-wave three-phase controlled rectifier with resistive or inductive load is shown in Fig. 6.1. There is one mathematical model valid for continuous and discontinuous conduction including the presence of a free wheeling diode. In each case though the parameters of the...

Products & Services
Power Meters
Power meters are used for high-accuracy measurements of power over a wide-frequency bandwidth, and from both AC and DC circuits.
Rectifier diodes are designed for use in rectification circuits. Rectifiers are used to convert AC to DC.
SCR Power Controllers
Silicon controlled rectifier (SCR) power controllers precisely regulate output power to resistive heating loads such as industrial furnaces and ovens. They generally operate on either zero-crossing or phase angle control.
Frequency-to-Current Converters
Frequency-to-current converters accept a frequency (an AC signal) and produce an output current whose value is a function of the input frequency.

Topics of Interest

7.1 Introduction The three-phase full-wave phase controlled rectifier is analysed in this chapter by considering an R-L load and continuous conduction. Voltage and current expressions, frequency...

8.1 Introduction In the normal operation of a full-wave three-phase converter with inductive load the output dc current is diverted from thyristor to thyristor and from phase to phase in a regular...

Chapter List Chapter 4: Analysis of the Single Phase ac to dc Phase Controlled Converter with R-L Load Chapter 5: The Single Phase Full-Wave Diode Rectifier - RC Load Chapter 6: The Three-Phase...

4.1 Introduction In the normal operation of a full-wave single phase converter the four thyristors conduct in two pairs: one from the upper group and one from the lower group. Thyristors TH1 and TH4...

Juan W. Dixon, Ph.D. Department of Electrical Engineering, Pontificia Universidad Cat lica de Chile Vicu a Mackenna 4860, Santiago, , Chile 12.1 Introduction Three-phase controlled rectifiers have a...