Hi all, welcome to the new course on power electronics. So before proceeding to this course, I expect the prerequisites are, I hope that you already have the idea about the basic electrical engineering, that is the network theory and along with that, I hope that you have some basic idea about the analog electronics. so complete details are not required i expect the basics details only about how the different devices will work and along with that i want the complete concept of the machines and power systems so that you will be able to understand what i am teaching properly so let us go to this course so as part of this course the name is telling power electronics this is the name of the course so this is having two different contradictory terms so first starting with the power The name itself is selling power that means we are dealing with the high power or higher value of the power. So the power engineering mainly deal with handling the high value of the power.
So we generate, transmit and distribute and utilize the high value of the power. So while transmitting the power, my major concern will be efficiency should be as maximum as possible for the case of power engineering when you are dealing with huge value of the power. Whereas coming to the electronics engineer, the electronics engineer mainly deal with the low power applications.
So here the value of the power is very less because generally this power will be in milliwatt and watts. So that's why efficiency is not the major concern for the electronics engineers. The major concern for the electronics engineer is to transmit the signal from the source to the load with the minimum possible distortion. So here my major concern is...
the distortion is the major concern here. So efficiency is not a major concern here. Let us take for example, if I take the example of a mic and the speaker.
So let us assume here there is a mic, a person speaks in the mic and this mic will be given to an amplifier. So amplifier what it do, whatever signal is given here, that signal will be amplified. and that will be given to the speakers.
So here my major concern is whatever signal is spoken at the mic, the maximum possible signal should receive the speakers so that maximum possible output will come. So here my major concern is you have to transmit the signal what a person is speaking here, whatever the person is speaking here, it should transmit distortion free to your speakers. you have to transmit the maximum possible power so under maximum power transfer condition we know the efficiency is only 50 percent but that doesn't matter in the case of electronic circuits but the disadvantage is the electronic circuits is they can be applied only for low power applications they are not designed for high power applications so now what i am going to do is a part of this course so we are dealing with power electronics what it is nothing but application of the electronic principles for the power conditions that means application of the electronic circuit for dealing the high power applications in order to improve the efficiency that is the major concern of power electronics so same thing i am summarizing here the electronics engineering deals with distortion less production transmission and reception of data and signals of very low power of the order of few milliwatts without much consideration of efficiency Here major concern is that distortion less only.
Distortion should be as minimized as possible. Efficiency is not the concern. But coming to the power engineering, it mainly concerned with the generation, transmission and distribution as well as utilization of the power and here the efficiency is the major concern for the power engineering. So the power electronics is a subject that concerns the application of electronic principles in power engineering.
to improve the efficiency of the system. So our major target is to improve the efficiency by using the electronic principles. So this basic power electronic system if you take this basically consists of these blocks.
There will be a source. So there will be a power converter circuit. So here only all the power electronic circuit will be there power converter circuit.
So this power converter circuit will produce the output and that output will be given to the load. So now coming to the source here the source input can be either voltage. current or frequency or any other parameter so this power converter will convert to some desired level so again the output can be either voltage current or some frequency parameter so it is having either ac or dc what i mean to tell this vif it can be either ac or it can be dc similarly the output can be either ac or dc it is supplied in such a way that my required characteristics are v are attained at your load and again some feedback will be taken from your load and that will be given to the control circuit.
So this control circuit will compare your load whatever you want to measure with the reference value and according to the conditions it will give a control signal to your power converter. So in order to explain this properly let us take the example of I want to change the speed of some motors that means there is a motor so I want to control the speed of the motor. We know that whenever you want to control the speed of an AC motor, the commonly used technique is V by F technique.
That means V by F ratio should be maintained constant. So that's why you will vary the value of V and you will vary the value of F using this power converter circuit. Because your input is AC having some constant voltage and constant frequency. So that will be converted to variable voltage and variable frequency such that V by F ratio is fixed constant. so that value is given to this load let us assume i set my motor speed should be equal to some 1400 rpm let us assume when the load is given by controlling this v by f output that 1400 rpm is not treated you got that 410 rpm so what should this control circuit do the control circuit will give the error signal to this power converter so here the error signal will be given according to the error signal the power converter will adjust the value of v and f so that the speed will go so in that way this feedback circuit will be useful so similar is the case i want to charge my battery of my mobile so again charging of the battery of my mobile what happens the input voltage will be given that input will be ac that ac will be converted to dc and dc nowadays the charging technology is coming fast charging technology so what it will do it will sense what is the voltage level of the battery of your mobile so that will be given as the feedback So depending on the battery voltage of your mobile, so there will be a reference value will be set here.
Accordingly, the error will be given to this power converter. And accordingly, this power converter will decide how much voltage and current will be applied across your battery. That means you might have seen there are two types of technologies.
In one technology, the voltage will vary. Voltage will be 5 volts and 9 volts. Other type of technology is there.
Voltage is constant, but current is variable. So depending on that this power converter will work and do the desired work. So this power converter circuit can be broadly classified into four categories based on what is the input and output of this power converter. So first one is AC to DC converter. These are also called as rectifiers.
So input will be AC and that AC is converted to DC. So the applications of this one is in traction because electric traction the input that is given will be equal to 25 kV AC. So that will be converted to DC and inside the DC series motors are used for mowing of your that traction or mowing of your train or train locomotive.
Now another example is a battery charges because battery charging also input is AC output will be DC. Now again for DC drives and excitation system of the synchronous machines for the synchronous machine also we need DC field therefore the DC field also we have to adjust the field also so that's why we convert AC to DC. So again, these rectifiers can be either control type or uncontrolled type.
Control type means we can adjust the output voltage as per the requirement. Uncontrolled means we cannot control the output voltage. Those are called as uncontrolled. So those things we are going to discuss.
Then the next one is DC to DC converters, which are also called as choppers. So the name comes because they choke the signal. That means if you are taking a DC signal, so this is my dc voltage let us assume this voltage is 10 volts i want to convert this voltage to 5 volts so what it will do it will chop it or it will cut it that means for a time of t by 2 this signal will be given again for the time of t by 2 signal will not be there again for t by 2 this signal will be given so this much time the switch will be on again off switch on and off then after that the smoothing filter will be used So because of the smoothing filter, the average value will now become equal to 10 divided by 2. So it becomes equal to 5 volts.
So in this way, they can do it. So this is called a step down. Similar way, you can step up the voltage also in the case of DC converters.
So those also called as the choppers only. So those also we are going to discuss. The applications of this DC-DC converters are DC drives, subway cars, battery driven vehicles, etc.
These are some of the examples. There is another application that is AC AC converter that means input is also AC, output is also AC. Again in this there are two types one is AC voltage regulator. So AC voltage regulator means input and output frequency will be same only voltage will be changed between the input and the output.
So these are mainly used in speed control of our household fans and pumps. If you take your home So nowadays electronic regulators are coming that electronic voltage regulators are nothing but these only AC voltage regulators. Input and output frequency is same. Like for example, if you are taking your input signal is this is my input.
So your output signal what will be there? This entire input will not be given to the output. You will decide at what instant your switch will be on. So it will follow the same thing in the positive as well as a negative half cycle. you can see here it is off for some duration here also off for some duration so automatically as your fan works based on the rms value so if you calculate the rms value for the signal rms value is decreased so automatically the speed will be decreased that means rms value of voltage given to your fan is decreased so depending on how much speed you want you can control at what instant your switch will be on by controlling the firing angle so this also we are going to see in detail Then after that, the second one is cyclo converters.
So the cyclo converter, the frequency is also variable along with the voltage. So these are called as cyclo converters. These are mainly used for V by F control of slow speed large AC drives.
So these are mainly used there. There is another type of converter. Both the input as well as input is DC and your output is AC.
That means it is converting from DC to AC. These are called as inverters. So these inverters have the application in induction heating.
Because for induction heating, because we know very high frequency signal. So for induction heating, UPS, HVDC, high voltage DC transmission, and the renewable energy systems such as the wind and solar energy, where the signal that is generated is DC in the case of solar. In the case of wind power, it is continuously changing frequency. Frequency is not constant because the power that is produced Frequency of power depends on the speed of the turbine because the speed of the turbine is not constant for the wind turbine. So that's why it will be converted to DC and the DC will be converted to 50 HAC and then synchronized to your grid.
So that is there also DC to AC converters are used. So along with the converters, because before discussing about these converters, we need the basics of power semiconductor devices and their characteristics. And after that, we will discuss about all these converters.
And after discussing these converters, we will see the applications part. That applications part which are there in the IES as well as the gate syllabus are DC and AC motor drives. So we are going to discuss about different DC and AC motor drives also.
So the basic books which I am going to refer for this subject are P.S. Bhimra and M.H. Rashid. And along with this, if I am referring any specific topic, any other book, I will mention in the respective lecture.
So before proceeding further. So I want to tell you how to use my channel because after preparing every 3-4 lectures, I will upload the material also. But many of the subscribers are always asking me, please send the material to so-and-so mail because every time I have to tell them, that's why I want to explain you how to download the material.
So for that, if you open my channel, your channel will be like this. So in this, if you go to the playlist, so here you can see all the playlist of different subjects. So in this, for example, let us assume I am going to my power system playlist.
so once you go into this playlist so these are my videos so whenever you play any one video let i assume for example i am playing one of the video so when you go to this video so below this video there will be a description you can see this is called as a description section if you click on show more so here i have provided the DC drive link if you click on this link so drive link will open there all the material will be available you can download the complete material from there I will go on updating the material after every three four lectures so now the doubt comes how this thing comes in the mobile because some of you may be using this thing in the mobile in the case of mobile if you want to get this description this section you have to click on the name of this lecture that means wherever the name of the lecture is coming you just click on the name of the lecture then it will expand and you will get this complete thing so here you have to click on link for the material from there you can download the complete material from there i will provide the pdf material after completing every three four lectures so in this way you can download the material and other things and if you have any doubts just go down and you can leave your comments in the comment sections so if you leave the comment here immediately i will get the notification i will revert back to your mail immediately So for example, some student has given me a comment, so I have replied to him. And whenever I reply to the comment there, so automatically you will get the notification in your mail also. You need not open the YouTube channel to check the comment. So notification will come to your mail also.
So next class onwards, we are going to start the power semiconductor devices first. So after that, we will proceed for different types of converters. So I hope the basic concept, how to download the material and other things are clear to you. if you still have any queries you can leave your comments in the comment section below i will answer to your queries from there thank you thank you very much