 Professor from WD Sallapur Department of Electronics Engineering. In this video we are going to look for the inductor filter. The objectives are at the end of this video student is able to describe the working of inductor filter and also he is able to analyze his performance. Now before we start the actual discussion, a power supply is electron electrical device that supplies a power to the load. The primary function of this power supply is to convert the input power into appropriate power required by the load. Actually the two types of power supplies are possible one is AC power supply or this is a DC power supply. AC power supply supplies AC power and whereas the DC power supply is supplying the DC power to the load DC power means a DC current and the DC voltage whereas we also can develop a DC power supply in which the input is a AC power that is supplied by the AC means. So that we have to first convert this AC power into DC power and for this we use normally rectifiers. Now rectifiers are having two types one is half wave or this is a full wave. Normally we prefer this full wave rectifier because it is having less ripple. Ripple is nothing but the amount of AC voltage or AC component available in the output. Now the input power is AC now so we are going to use rectifier again I said that it has got two output components which is DC and the AC. DC is the required component we have to supply to the load and we have to remove all the AC component coming to the load here. Now how we are going to remove this unwanted AC component and for this we are going to use a circuit called as a filter. Actually the filter circuit is created by using some electronic components that is either inductor or capacitor or we also can use both of these components together. So in this video we are going to mainly focus on the inductor filter. Now inductor filter uses inductor and we are going to connect this component which also called as a filter component in the series of the load. Now again question comes why we only connect this inductor in the series with the load. Now we know here the DC power is supplied by rectifier it has got two components one is AC and other is DC and we know inductor is a component that gives a very high impedance to the flow of AC and whereas he passes the DC component. As I said here the output of rectifier is having DC and AC component. So inductor passes all the DC to the load that we require and this inductor offers very high impedance to the flow of AC current so that all the AC power which is supplied by the output of rectifier is dropped across the inductors which confirm that the very small amount of AC power that is AC current is passed through the load here. It means that with the help of this internal filter we can create a very high amount of DC power and we are going to create a very small amount of AC power. This AC power is normally called a ripple so in the load we normally find a ripple voltage it is across the load we also are going to find out the ripple current is flowing through the load. So filter is that circuit that reduces the ripple and that passes the DC here that's why we are going to connect this inductor in the series of the load this also is called as a choke filter. Let us see a diagram here you see that the inductor is connected in series with the load and the current which is flowing in the load is given as is a sum of IDC and the IC. IDC is useful current and IC is unwanted ripple current. Now simply by diagram is like this here just focus on waveform the waveform shows you three different body it is full rectified sand wave is output of rectified circuit then the output across the load is shown again by a sand wave you will see that the peak of the full rectified sand wave and the peak of the voltage across the load are not matching there is a difference between their peaks here it is only because the current which is flowing across the inductor or through the inductor is lagging the voltage here and that's why the peaks are not matching and we also see one dotted line is shown here it shows you the DC voltage available across the load and currently the value is given as 2v that is a maximum voltage across load is given as 2v max by pi. Now the output of rectifier circuit is not defined by a Fourier series you will see that there are two components one is 2vm by pi and whereas there is one more component that consists of some terms which are having a term in the form of so in this equation we see that the terms with 2 omega 6 omega and so on the terms with this omega normally called as the harmonics here so we say that for the current equation we are having second harmonics and the sixth harmonic is available in the output here. Now normally seen that the higher order harmonics are normally are going to drop to 0 rapidly and they are not going to contribute much across the load here so normally to simplify the solution here we normally neglect the third and higher harmonics in the equation so that we are going to redefine the voltage across the load as 2vm by pi minus 4vm by 3 pi into cos 2 omega d in this we are going to neglect the resistance of diode resistance of the choke and resistance of secondary of the transformer. Now friends last equation show that it has got two components one is DC so I will define this DC voltage in the form of DC current here now we know here IDC is defined as the VDC upon RL because VDC is the voltage across load so that IDC can be defined as 2vm by pi RL similarly we also can define the AC component here from the equation VAC is given as 4vm by 3 pi into cos 2 omega t and this voltage is applied across a series combination of inductor and resistance here so we can define the AC current which is flowing through inductor and the resistance as VAC upon the impedance of series combination of inductor and resistor combination there so it is defined as under root RL square plus 2 omega l bracket square here we use the frequency component as 2 omega because in the equation we have only got a term which is 2 omega that is a second harmonics here also as I said in the waveform the peak of the voltage across rectifier and the peak of the voltage across load is not matching there is a lag so in this equation that is AC component is redefined as by this equation and this equation in the cos term we are going to find out a phi now this phi is defining the angle of lag between the input voltage and the output voltage here and it is because of the inductor in the middle between the output of rectifier and the load here so we can redefine the load current which is flowing across the load is AC current and DC current combination here so I define this as I L equals to a DC component defined by 2vm by pi RL and minus a term that has got 2 omega t factor it is a AC factor or AC term we can say now here we are trying to derive the ripple factor for this inductor filter now we know the formula to find out ripple factor is given as the RMS failure of AC component of the current divided by the DC component of the current here now here we are going to use the RMS failure of AC component so it is defined as I RMS that is I RMS upon IDC now from previous equations as we all know IDC is nothing but 2vm by pi RL and whereas I RMS that is same as I AC RMS here so it is defined as I AC upon root 2 so that this term is coming as as given here you are going to find an extra term as a root 2 in denominator so we can write this ripple formula in this way here mind this equation normally the value of 4 omega square L square upon RL square is very high as compared with the 1 because we choose the value of inductor such a way that it is offering us a very high reactance path to the flow of AC component here so that we are going to neglect one from the equation and we are going to redefine this value of this ripple factor as RL upon 3 root 2 omega L now this factor shows you the performance of inductor filter now friends just think that why we use this inductor filter only for heavy loads so we can define in last slide the performance of inductor filter now from this equation we see that ripple is inversely proportional to the inductor value that is its inductor magnitude and secondly ripple is always smaller when the load is smaller friends these are my references I hope that you understand the performance of inductor filter and its derivation of ripple factor thank you thank you for watching the video thanks very much