# Ripples in the pulsating D.C.

1. Apr 14, 2014

### neeraj kaira

Which value of capacitor should i use in rectification so as to remove the ripples from the pulsating d.c? Having 50 hz 12 volts ..any formula related with ripples and capacitance?

Last edited: Apr 14, 2014
2. Apr 14, 2014

### Jony130

You can use this equation

C = Q/V = ( I * t )/V

where
t - discharge time 1/50Hz (20ms) for half wave rectifier and 1/100Hz (10ms) for full wave rectifier or 1/60Hz and 1/120Hz for countries with 60Hz mains.
V - capacitor ripple voltage

3. Apr 14, 2014

### neeraj kaira

Oh thanks i'll use this formula lets c...

4. Apr 14, 2014

### neeraj kaira

And what's the value of t for bridge rectifier? Same as full wave ?

5. Apr 14, 2014

### Jony130

Yes, the same as for full wave.
t = 10ms

6. Apr 14, 2014

### Staff: Mentor

7. Apr 14, 2014

### neeraj kaira

Thanks and m one more ques please why we mostly use capacitor filter and inductor not ??? Inductor also blocks high frequency waves...its only because capacitor is easy to fabricate in the circuits?

8. Apr 15, 2014

### Staff: Mentor

Inductors are comparatively heavy and expensive. They can hum audibly. Also, the capacitor input filter is a peak detector, whereas the inductor is an averaging filter so delivers a lower output voltage for the same transformer voltage input.

You'll still need a filter capacitor to accommdate load variations (to realize a low-impedance), because the inductor has a steady-current characteristic (a high impedance characteristic).

Last edited: Apr 15, 2014
9. Apr 16, 2014

Ok thanks :)