Which Capacitor Value Removes Ripples from 50Hz 12V Pulsating DC?

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Discussion Overview

The discussion revolves around selecting an appropriate capacitor value for rectification to minimize ripples in a 50Hz, 12V pulsating DC signal. Participants explore formulas related to capacitance and ripple voltage, as well as the comparative use of capacitors and inductors in filtering applications.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant inquires about the capacitor value needed to remove ripples from a pulsating DC signal and requests related formulas.
  • Another participant provides a formula for capacitance, C = Q/V = (I * t)/V, specifying variables such as load current (I), discharge time (t), and ripple voltage (V).
  • There is a question about the discharge time (t) for a bridge rectifier, which is confirmed to be the same as for a full wave rectifier (10ms).
  • A participant shares a link to an image that may help visualize the rectification process.
  • One participant asks why capacitors are preferred over inductors for filtering, suggesting that inductors also block high-frequency waves.
  • Another participant explains that inductors are heavier, more expensive, and can produce audible hum, while capacitors serve as peak detectors and are necessary for accommodating load variations.

Areas of Agreement / Disagreement

Participants generally agree on the use of the provided formula for capacitance and the discharge time for bridge rectifiers. However, there is a discussion regarding the advantages and disadvantages of using capacitors versus inductors for filtering, indicating multiple perspectives on the topic.

Contextual Notes

The discussion includes assumptions about the load current and ripple voltage, which are not explicitly defined. The effectiveness of different filtering methods remains a point of exploration without a definitive resolution.

Who May Find This Useful

Individuals interested in electronics, particularly those working with power supply design, rectification processes, and filtering techniques, may find this discussion relevant.

neeraj kaira
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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:
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You can use this equation

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

where
I - load current
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
 
Oh thanks i'll use this formula let's c...
 
And what's the value of t for bridge rectifier? Same as full wave ?
 
neeraj kaira said:
And what's the value of t for bridge rectifier? Same as full wave ?
Yes, the same as for full wave.
t = 10ms
 
This kind of image usually helps to visualize what is going on...

http://macao.communications.museum/images/exhibits/2_16_0_12_eng.png
2_16_0_12_eng.png
 
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?
 
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:
Ok thanks :)
 

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