Question

Half controlled converter can operate in how many quadrant in v-i plane

Answer 1

Answer:

INTRODUCTION TO CONTROLLED RECTIFIERS

Controlled rectifiers are line commutated ac to dc power converters which are used to convert a fixed voltage, fixed frequency ac power supply into variable dc output voltage.

line-commutated-converter

Type of input: Fixed voltage, fixed frequency ac power supply. Type of output: Variable dc output voltage

The input supply fed to a is ac supply at a fixed rms voltage and at a fixed frequency. We can obtain variable dc output voltage by using Controlled rectifiers. By employing phase controlled thyristors in the circuits we can obtain variable dc output voltage and variable dc (average) output current by varying the trigger angle (phase angle) at which the thyristors are triggered. We obtain a uni-directional and pulsating load current waveform, which has a specific average value.

The thyristors are forward biased during the positive half cycle of input supply and can be turned ON by applying suitable gate trigger pulses at the thyristor gate leads. The thyristor current and the load current begin to flow once the thyristors are triggered (turned ON) say at ωt= α. The load current flows when the thyristors conduct from ωt= α to β . The output voltage across the load follows the input supply voltage through the conducting thyristor. At ωt= β, when the load current falls to zero, the thyristors turn off due to AC line (natural) commutation.

In some bridge circuits the conducting thyristor turns off, when the other thyristor is (other group of thyristors are) turned ON.

The thyristor remains reverse biased during the negative half cycle of input supply. The type of commutation used in circuits is referred to AC line commutation or Natural commutation or AC phase commutation.

When the input ac supply voltage reverses and becomes negative during the negative half cycle, the thyristor becomes reverse biased and hence turns off. There are several types of power converters which use ac line commutation. These are referred to as line commutated converters