In a single phase full wave ac regulator the rms value of load current...
Introduction:
In a single phase full wave AC regulator, the thyristors are used to control the average value of the load current. The load in this case is purely resistive, which means it does not have any reactive component. We need to determine the relationship between the load current and the thyristor current in terms of their average and RMS values.
Explanation:
In a single phase full wave AC regulator, the thyristors are used to control the average value of the load current. When the thyristors are turned on, they allow the current to flow through the load. When they are turned off, the current through the load becomes zero. This on-off switching of the thyristors creates a pulsed current waveform.
Average Load Current:
The average value of the load current can be calculated by taking the time integral of the instantaneous load current over one complete cycle and dividing it by the time period of the cycle. Since the load is purely resistive, the instantaneous load current is sinusoidal in nature. The average value of a sinusoidal waveform over one complete cycle is zero. Therefore, the average load current will be zero.
RMS Load Current:
The RMS value of the load current is the square root of the average of the squared instantaneous values of the load current over one complete cycle. For a purely resistive load, the RMS value of the current is given by the formula: RMS current = Peak current / sqrt(2). In this case, the RMS load current is given as 20 A.
Average Thyristor Current:
The average value of the thyristor current can be calculated in a similar manner as the average load current. However, since the thyristors are not ideal switches, they have a certain voltage drop and some losses associated with them. This means that the average thyristor current will be less than the average load current. Therefore, option A is incorrect.
RMS Thyristor Current:
The RMS value of the thyristor current can be calculated using the same formula as the RMS load current. However, since the thyristor current is pulsed, it will have a higher RMS value compared to the load current. This is because the RMS value is calculated by taking the square root of the average of the squared instantaneous values of the current. Since the thyristor current is non-zero only during the on-state of the thyristors, the instantaneous values of the thyristor current will be higher compared to the load current. Therefore, the RMS thyristor current will be more than 20 A. Option D is incorrect.
Conclusion:
Based on the above explanation, we can conclude that in a single phase full wave AC regulator with a purely resistive load, the average thyristor current will be less than 20 A, and the RMS thyristor current will be more than 20 A. Therefore, option B is correct.
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