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What is Ripple and Ripple Factor?Formula of Ripple Factor

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 ripples in the DC current is called the current ripples.

Reasons of ripples in DC output?

The rectification compents 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 the ripples is impossible. Yes,we can reduce the ripples to a great extend by filtering the rectified DC output voltage.

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

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

Ripple Factor Definition

The ratio of r.m.s. value of a.c. component to the d.c. component in the rectifier output is known as the ripple factor.

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

Ripple Factor Formula

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

Derivation of Ripple Factor Formula 

The rectified output does not have pure DC component but it has AC component as well. The AC component availble 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 iLhas both AC ripple component and DC compont(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 ripple current is follows.