Question

A 1-\(\phi\) AC voltage controller feeds a load resistance of \( R \). If firing angles of two switches are off set at \( 180^\circ \), then rms value of input current is

• A. Equal to half the rms value of load current
• B. Greater than rms value of load current
• C. Equal to rms value of load current
• D. Less than rms value of load current

Hint:

With 180° phase shift firing in resistive loads, input current appears only in alternate half-cycles.

Answer 1

The Correct Option is A

For purely resistive loads in an AC voltage controller, when switches are triggered \( 180^\circ \) apart, conduction occurs only in alternate half-cycles. Hence, input current is present only half the time: \[ I_{\text{in, rms}} = \frac{I_{\text{load, rms}}}{\sqrt{2}} \times \sqrt{2} = \frac{1}{2} I_{\text{load, rms}} \]