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.
Type of input: Fixed voltage, fixed frequency ac power supply.
Type of output: Variable dc output voltage
The input supply fed to a controlled rectifier 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 controlled
rectifier 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 controlled rectifier 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 controlled rectifier 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.
used to convert a fixed voltage, fixed frequency ac power supply into variable dc
output voltage.
Type of input: Fixed voltage, fixed frequency ac power supply.
Type of output: Variable dc output voltage
The input supply fed to a controlled rectifier 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 controlled
rectifier 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 controlled rectifier 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 controlled rectifier 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.
No comments:
Post a Comment