Question

To reduce the ripples in a rectifier circuit with capacitor filter ______.

1. R_L should be increased.
2. input frequency should be decreased.
3. input frequency should be increased.
4. capacitors with high capacitance should be used.

Options

• a and c

• b and d

• a, c and d

• b, c and d

Answer 1

a, c and d

Explanation:

The ripple factor may be defined as the ratio of r.m.s. value of the ripple voltage to the absolute value of the DC component of the output voltage, usually expressed as a percentage. However, ripple voltage is also commonly expressed as the peak-to-peak value. The ripple factor (r) of a full wave rectifier using a capacitor filter is given by

`r = (0.236 R)/(ωL)`

Where L is the inductance of the coil and ω is the angular frequency.

or Ripple factor can also be given by

`r = 1/(4sqrt(3)v R_LC_V)`

i.e., `r  ∝ 1/R_L` ⇒ `r ∝ 1/C, r ∝ 1/V`

The ripple factor is inversely proportional to R_L, C and v.

Thus to reduce r, R_L should be increased, input frequency v should be increased and capacitance C should be increased.