What is a Ripple Factor and Its Derivations
When the fluctuation occurs within the output of the rectifier then it is known as ripple. So this factor is essential to measure the rate of fluctuation within the resolved output. The ripple within output voltage can be reduced by using filters like capacitive or another kind of filter. In most of the circuits like rectifiers utilizes a capacitor within parallel of thyristor otherwise diodes to work as a filter within the circuit. This capacitor helps to decrease the ripple within the rectifier output. This article discusses an overview of the ripple factor (R.F) which includes its definition, calculation, its significance, and R.F using half-wave, full-wave, and bridge rectifier.
What is Ripple Factor?
The rectifier output mainly includes the AC component as well as the DC component. The ripple can be defined as the AC component within the resolved output. The A.C component within the output is unwanted as well as estimates the pulsations within the output of the rectifier. Here the ripple voltage is nothing but the AC component within o/p of the rectifier. Similarly, the ripple current is an AC component within o/p current.
The definition of the ripple factor is the ratio of the AC component’s RMS value and the DC component’s RMS value within the output of the rectifier. The symbol is denoted with “γ” and the formula of R.F is mentioned below.
Nature of Rectifier Output
Nature of Rectifier:- It has already been discussed that the output of a rectifier is pulsating d.c. as shown in Fig. 6.37. In fact, if such a waveform is carefully analyzed, it will be found that it contains a d.c. component and an a.c. component. The a.c. the component is responsible for the *pulsations in the wave. The reader may wonder how a pulsating d.c. voltage can have an a.c. component when the voltage never becomes negative. The answer is that any wave which varies in a regular manner has an a.c. component.
The fact that a pulsating d.c. contains both d.c. and a.c. components can be beautifully illustrated by referring to Fig. 6.38. Fig. 6.38(i) shows a pure d.c. component, whereas Fig. 6.38 (ii) shows the *a.c. component. If these two waves are added together, the resulting wave will be as shown in Fig. 6.38 (iii). It is clear that the wave is shown in Fig. 6.38 (iii) never becomes negative, although it contains both a.c. and d.c. components. The striking resemblance between the rectifier output wave shown in Fig. 6.37 and the wave is shown in Fig. 6.38 (iii) may be noted. It follows, therefore, that a pulsating output of a rectifier contains a d.c. component and an a.c. component.
What is Ripple Factor of Full Wave Rectifier
The output of a rectifier consists of a d.c. component and an a.c. component (also known as ripple). The a.c. component is undesirable and accounts for the pulsations in the rectifier output. The effectiveness of a rectifier depends upon the magnitude of a.c. component in the output; the smaller this component, the more effective is the rectifier.
The ratio of r.m.s. value of a.c. component to the d.c. component in the rectifier output is known
as ripple factor i.e.
Therefore, the ripple factor is very important in deciding the effectiveness of a rectifier. The smaller the ripple factor, the lesser the effective a.c. component and hence more effective is the rectifier. Mathematical analysis. The output current of a rectifier contains d.c. as well as a.c. component. The undesired a.c. the component has a frequency of 100 Hz (i.e. double the supply frequency 50 Hz) and is called the ripple (See Fig. 6.39). It is a fluctuation superimposed on the d.c. component.
By definition, the effective (i.e. r.m.s.) value of total load current is given by :
It is clear that a.c. component exceeds the d.c. component in the output of a half-wave rectifier.
This results in greater pulsations in the output. Therefore, half-wave rectifier is ineffective for conversion of a.c. into d.c.
For Ripple factor of full-wave rectification
In full-wave rectification,
This shows that in the output of a full-wave rectifier, the d.c. component is more than the a.c.
component. Consequently, the pulsations in the output will be less than in half-wave rectifier. For
this reason, full-wave rectification is invariably used for conversion of a.c. into d.c.
Example 6.22. A power supply A delivers 10 V dc with a ripple of 0.5 V r.m.s. while the power
supply B delivers 25 V dc with a ripple of 1 mV r.m.s. Which is a better power supply?
Solution. The lower the ripple factor of a power supply, the better it is.
Comparison of Rectifiers
A comparison among the three rectifier circuits must be made very judiciously. Although bridge
circuit has some disadvantages, it is the best circuit from the viewpoint of overall performance. When the cost of the transformer is the main consideration in a rectifier assembly, we invariably use the bridge circuit. This is particularly true for large rectifiers which have a low-voltage and a high-current rating.
Why Ripple Occurs?
Whenever the rectification occurs through the rectifier circuit then there is no chance of getting accurate DC output.
Some variable AC components are frequently happening within the rectifier’s output. The circuit of a rectifier can be built with diodes otherwise thyristor. The ripple mainly depends on the elements which are used within the circuit.
The best example of the full-wave rectifier with a single phase is shown below. Here the circuit uses four diodes so the output gets like the following waveform.
Here we estimated the accurate DC o/p waveform but we cannot get like that due to some ripple within the output and it is also called pulsating AC waveform. By employing a filter within the circuit, we can get almost DC waveform which can diminish ripple within the output.
Some equipment can work by ripples but some of the sensitive types of equipment like audio as well as the test cannot work properly due to the effects of high-ripple within the supplies. Some of the ripple effects of equipment mainly occur due to the following reasons.
- For sensitive instrumentation, it affects negatively
- Ripple effects can cause errors within digital circuits, inaccurate outputs in data corruption & logic circuits.
- Ripple effects can cause heating so capacitors can be damaged.
- These effects initiate noise to audio circuits
Thus, this is all about the ripple factor. From the above information finally, we can conclude that generally a rectifier is used to convert the signal from AC to the electrical signal. There are various types of rectifiers available in the market which can be used for rectification such as full-wave rectifier, half-wave rectifier and bridge rectifier. All these have dissimilar efficiency intended for applied i/p AC signal. The rectifier’s ripple factor and efficiency can be measured based on the output. Here is a question for you, what is the ripple factor of full wave rectifier with capacitor filter?
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Reference: Principles Of Electronics By V K Mehta And Rohit Mehta