Question

A single-phase voltage controller has input voltage of 210V and load R = 10 ohm. For 4 cycles on and 5 cycles off, the rms output voltage is

• A. 140 V
• B. 70 V
• C. 210 V
• D. 100 V

Hint:

In voltage controllers using on-off cycles, RMS voltage is found using the square root of the duty cycle multiplied by the input voltage.

Answer 1

The Correct Option is A

The output voltage in such a case can be calculated using the duty cycle method. For 4 cycles on and 5 cycles off, the duty cycle \( D \) is: \[ D = \frac{4}{4 + 5} = \frac{4}{9} \] The RMS output voltage \( V_{rms} \) is given by: \[ V_{rms} = V_{in} \times \sqrt{D} = 210 \times \sqrt{\frac{4}{9}} = 210 \times \frac{2}{3} = 140 \text{ V} \]