WELCOME TO THE PRESENTATION Dr. S. Narasimha TKRCET By Professor, Dept of E.E.E TKRCET

PHASE CONTROLLED RECTIFIERS

Single-Phase Half-Wave Converter Average Load Voltage =

With Inductive Load Average value of Load Voltage:

Effect of Free Wheeling Diode : Main Functions : It prevents reversal of load voltage except for small diode voltage drop. It transfers the load current away from the main rectifier, thereby allowing all of its thyristors to regain their blocking states.

Single-Phase Full-Wave Converter Basic Configurations Mid-Point Converters Bridge Converters

Mid-Point Converters With R-Load Average dc voltage: Avg.Load current is

With Inductive Load :

Some Conclusions from the given equation : The highest value of this voltage will be when the firing angle is zero i.e. = 0°. This voltage is zero when = 90°. Meaning that the load voltage will contain equal positive and negative areas, giving zero output voltage. This voltage is negative maximum when = 180°.

For Firing angle 300

For Firing angle 900

For Firing Angle 1500

Effect of Free Wheeling Diode : Average dc voltage : Average dc current:

Bridge Converter(B-2 connection) : R-Load :

With R-L Load:

Mode 1 Rectifying Mode :

Mode 2 Inverting Mode

Line Commutated Inverter :

Advantages of Single-Phase Bridge Converter over Mid-Point Converter SCRs are subjected to a peak-inverse voltage of 2 Em in mid-point converter and Em in fully controlled-bridge converter. Hence, for the same voltage and current ratings of SCRs, power handled by mid-point configuration is about half of that handled by bridge configuration. In mid-point configuration, each secondary should be able to supply the load-power. As such, the transformer rating in mid-point converter is double the load-rating. This, however, is not the case in the single-phase bridge converter.

Half Controlled Bridge Rectifier : R-Load

With R-L load :

Fully Controlled converter Comparison of Half Controlled Converter with Fully Controlled converter Since half the thyristors are replaced by diodes, a half-controlled converter costs less than a fully-controlled converter. The periods of the negative-voltage “swing” at the d.c. terminals obtained with fully-controlled bridge-circuit are replaced by “freewheeling” periods of zero voltage in the half-controlled circuit. The elimination of the negative swings of voltage at the d.c. terminals is advantageous because it results in a reduction of the ripple voltage, with correspondingly reduced filtering requirements. In half-controlled bridge-circuit, the average d.c. terminal voltage can be continuously controlled from maximum to virtually zero with an increased control range of the firing angle .

Due to the freewheeling action with half-controlled bridge-circuit, power factor is improved in half-controlled-converters. The a.c. supply-current is more distorted due to its zero periods with half-controlled circuit, compared to fully-controlled bridge-circuit.

Three-Phase Controlled Converters : Three-Pulse Converter Six-Pulse Converter

Three-Phase Half wave Converter : R-Load : With resistive load, there are two modes of conduction. They are: (1) Continuous conduction mode for . (2) Discontinuous conduction mode for .

Three-Phase Fully Controlled Bridge Converter : With R-Load

Continuous Conduction Mode : Discontinuous Conduction Mode :

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