What is Ripple and Ripple Factor? Formula of Ripple Factor

Ripple factor is the ratio of AC Plus DC components to DC components in the rectified waveform. In this article, we will learn what is ripple, ripple factor, ripple factor formula & its derivation.

Factoring Expressions
Factoring Expressions

What is Ripple?

When the AC waveform is rectified with a rectifier unit, the rectified output is not perfectly DC rather the DC output has pulsating component called AC components. The pulsating components present in the DC output voltage is called the voltage ripples, and the pulsating components in the DC current is called the current ripples.

Reasons of ripples in DC output?

The rectification components like diode, silicon controlled rectifier, Insulated gate bipolar transistor cause the DC output of pulsating nature. The ripples are undesirable in the DC output, however complete elimination of it is impossible. Yes, we can reduce these to a great extend by filtering the rectified DC output voltage.

If we observe the rectified DC output of the full wave rectifier, we find that rectified DC output is not perfectly DC rather than the rectified DC voltage or current has AC components.

waveform of ripples in dc

The output of the full wave rectifier has pulsating voltage. The average or DC voltage reduces due to presence of pulsating voltage in the rectified output voltage or current. The full wave rectifier has less ripples than a half wave rectifier.

Ripple Factor Definition

The ratio of RMS value of AC component to the DC component in the rectifier output is known as the ripple factor.

ripple factor definition

This factor is very important parameter for assessing the effectiveness of the rectifier. The lower ripple factor value shows that the ripples in the DC output is less and the efficiency of the rectifier is better. and, the higher value shows that there are more fluctuating ac component present in the rectified output.

Ripple Factor Formula

The RMS. value of rectified DC voltage is the vector sum of the AC components and DC component in the rectified output. 

ripple factor formula

Derivation of Ripple Factor Formula 

The rectified output does not have pure DC component but it has AC component as well. The AC component available in the rectified DC cause lower rectification efficiency. The load current has both AC and DC component. Let the load current is IL and the load current iL has both AC component and DC component(Idc).

Ripple = IL– Idc  = VL– Vdc  

Here, iL and vL are the output current and voltage through the load connected at the terminals of rectifier. Similarly, Vdc and Idc are the average value of load voltage and current. The RMS value and the average value of the load current is as given below.

The calculation of RMS value of the rectified current is follows.  

derivation of ripple factor formula
derivation of ripple factor formula
Derivation of ripple factor formula

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