how to test transformer using multimeter

 

how to test transformer using multimeter

 Today I will explain, how to test transformer using multimeter. I have one transformer here. That is shown here. It has one primary 230 volt. It has one secondry 180 volt. That has one tapping also. And they are isolated with each other. To check that, We measure 6 types of resistance, in this transformer. First is P,  P means, resistance of primary winding. It will not show short, because wire is very long. 100s of turns wii be there. Some value will come, but it will not be open. Similarlly S1 & S2, S1, we will measure the resistance of this , winding from here to here. That also will not be short, it will show some value. Then S2, we will measure resitance between this & this. Then P & S. In between primary & secondry, we will measure the resistance. It has no connection. It will show open. If there is any failue of insulation, It will not show open. Then, this is core, We measure the resistance primary to core. This is primary winding, this is core. In between these two, we measure resistance. That also will come open. If there is some shorting or insulation breakup Then this will not come open. So we will know, it is damage or not. Similarlly secondry & core. This is secondry. This is core. In between this & this, We will measure the resistance. That again should come open. Now, I have connected my multimeter, across primary. Here. This is showing 65.2 volt, this is not showing zero. This is showing some value. We will write 65.2 volt. Now I have another small transformer. We will check, the primary winding resistance of this also. So I will connect like this, here. Now this is showing open. Open does not means, that this is bad. Open means, I have set value 200 ohms. You see, value of resistance is more than 200 ohm. I will increase the scale. Now showing 919 ohm. So this value much much more, than this. Because this transformer is of small rating. This is 30 VA. This is about 10 VA. 2nd thing, this is very good industrial grade transformer. This is normal commercial transformer. So, after connecting, your multimeter here, We have to change the scale. Just it is showing open, does not mean, it is bad. There is a possibility, That resistance of this winding may be higher. Only thing, it should not be open. Now, I am measureing resistance, across this. This is this terminal. This terminal is this. So resistance across this is, coming 55.8 ohm. I will write 55.8 ohm. Now I will measure the resistance between these two. 160 volt winding. This is 160 volt winding. This is common. So I will change. Now resistance is comming 49.4 ohm. You are seeing. Here resistance is higher 65 ohm. Here resistance is lower. Because turns are more here. The more the turns means, the higher the resistance will be. Lesser the turns, resistance will be less. Across this, turns are very less. They will be for only 20 volt difference. We will measure here also. Let us see how much comes. It is just 7.3 ohms. From here to here, Resistance is very low, only 7 ohm. Because turns are very less. Now, I have connected my multimeter, at this point and this pont, between primary & secondry. This is showing open, open does not mean, That this is OK. Because I have set value 200 ohm. We have to set at high value. Now I have set at 2000K. Still it is showing open, means, In between this & this, It is perfect open. There is no insulation failure. See here. Now I will measure resistance, betwen primary winding & core. Primary is this. Core, this is core. But this core is connected here using a terminal. Industrial transformer will have a connection like this. The core terminal is brought here. And then earth terminal is shown here. So I measure between this ( primary winding, ) and this core point. See, this is showing open. This scale is at higher range. I am checking this primary winding & core. This is showing open means, no insulation failure in primary winding. Now I will check secondry & core. This is core. This point, I will change to secondry. Again showing open. So all 3 are open. This means, there is no insulation failure here or here. Now here, I have shown, between primary & secondry, there will be open. This is called isolating transformer. If it is auto transformer like this, Then primary & secondry are shorted in auto transformer. There is no isolation. Then it will not be open. It will show some value. Now to measure turn ratio, We have to give AC here. With this way, we can not measure. At primary, we will give AC voltage here. This value will depend upon the rating of this transformer. To secodry, we connect a multimeter. And measure the voltage here. And this voltage devided by this voltage, will give this turns, devided by this turns. This is for one tap. For another tap, We have to connect multimeter like this. This voltage, devided by this voltage, will be equal to this turns, devided by this turns. This method, what I have shown, If you check the transformer in the lab or house, that will be not full tests. In production, in companies, They do so many other tests, not only these tests. Today this much only. 

What is zinar diode & working as a voltage regulator

  Welcome. Today I will explain function of zener diode & its applications. This is symbol of zener diode. It has 2 terminals, one is anode, one is cathode. This is special type of diode. In this if we flow the current in forward direction, Forward means anode to cathode, current is flowing like this. Then it behaves like normal diode. But if we apply the voltage in reverse direction, Reverse means, cathod voltage +ve and anode voltage negative, or cathode voltage more than anode voltage. And voltage in reverse direction, becomes equal or greater than break down voltage of zener diode. Then current starts flowing. So in zener diode, current can flow in both the directions. This is characteristic curve of zener diode. This is V. This is I. This operates in 2 ways. This side is +ve biasing. This side is negative biasing. This side it behaves like normal diode. This side it behaves like zener diode. In this side, when voltage exceeds more than 0.7 V, say for silicone diode, current will increase suddenly. But we will discuss here. Zener diode behaviour. In reverse side ,when we apply the voltage, small leakage current flows. When reverse side voltage crosses, break down voltage, this is breakdown voltage, Then current will increase suddenly. And the voltage remains less or more constant. Zener diode has one dynamic resistance. Which is equal to delta V/ delta I. Suppose we take 2 point A & B, This line is not vertical, it has some angle, you see like this. This ∆V is the voltage difference between A & B. And ∆I is the difference of current at point A & B. Ratio ∆V/∆I is called the dynamic resistance. It can be10 ohm, 20 ohm, 100 ohm & so on. Now we come to specifications. This is one example. Say zener diode voltage is 5.6 volt. If you see the data sheet, There will be tolerance say +/- 5%. So 5.6 volt will not be correct value, When you measure, it may be 5.6, + 5% or minus 5% or in between. If you want accurate value, You can take 5 or 10 numbers of zerer diodes, measure the value, and select one which has closure value. Now zener diode has 3 currents. One is test current. One is normal current. 3rd is surge current. Test current means, you will get 5.6 volt at this current. This is the test current. For example if 45mA flows in a zener diode, Voltage measured across this will be 5.6 V. 2nd is 160 mA, Which is continous current it can take. 3rd is surge current. Now you see this current 810 mA, is almost 5 times, compare to 160 normal current. This means for short time, It (zener) can take much more current, say 810mA, this is just example. 810 mA for 10 mSec only, not for longer time. Then power loss. Suppose this zener diode has 5.6 V, Current flowing in this is Iz. Loss will be VzIz. Nor this loss or this current. Current flowing in this, that will decide the loss. I have written 2 figures. 900 mW & 1300 mW. In this case, This zener diode is rated 1300mW at 25 degree. That is this point. This is power derating curve. This is temperature. This is power. Till 25, it is 1300 mW. If you increase the ambient temperature, You have to derate. It can not take 1300 mW. It can take less. For example at 70 degree, It can take only 900 mW. This is just example. So we have to derate. One more thing is there, When they define this power, or this current, They define lead length also. You have to see data sheet carefully. Now we come to applications. This is list of 8 applications. Out of 8, two are shown here. Remaining 6 are in other sheet. Now here I have shown, Zener diode application in waveform clipper. I have connected 2 zener diode in series. But polarity is reverse. In one case cathode is at top. Another case anode is at top. So total voltage will be this voltage 5.6V + this drop 0.7V=6.3V. This is resistor to limit the current. When we give input voltage AC, Output voltage will not exceed more than 6.3V. Output will be red color like this. This drop, this voltage will be 6.3V. Then zener diode application in voltage shift. This is voltage. This is time. Green color is input voltage. This volatge will be always less than this equal to this drop. Suppose at this point, at input voltage is this. So output voltage will be this voltage, minus this zener diode drop. So we get this. Now this is another application of zener diode, in voltage regulation. I have connected one resistor here. This resistor is connected to limit the current in this. And ouput voltage will be equal to zener diode voltage. And current flowing in load will be Vz/RL. But limitation of this circuit is, To much variation in load is not allowed. It has limitation. To improve that this is better way. Here I have connected one transistor. NPN transistor. In zener diode, current flows like this. Now suppose zener diode voltage is 5.6 V, Then voltage at this point at output will be equal to this voltage minus this voltage, Vbe voltage. Suppose Vbe voltage is 0.6 V, Then voltage at this point will be You will get 5 volt here, not 5.6V in this load connected. You can select bigger size of NPN transistor. In this case load variation can be to much. It has lot of range to change the load. When we use this kind of circuit, Then load current flows like this, through transistor. This is load current. And power loss across this transistor, will be load current multiply by drop across transistor Vce. Now this is another application of zener diode, in over voltage protection. This is thyristor. I have connected one zener diode in gate. This resistor is connected to suppress noise. When voltage across this, become equal or more than this zener diode, Zener diode will conduct. And the gate current will flow like this. Because of this gate current, this thyristor will trigger. and this will become short. It will not be fully short because there will be drop of thyristor small drop. Now current flows like this. Now there are 2 ways we can use this. We connect a fuse here. When this becomes short, very high current will flow. And fuse here will blow. 2nd application is, we do not want fuse to blow. We want zero volt itself. Whenever voltage across this, becomes equal or more than this, we want zero volt. In that case fuse is not required. In my one project we wanted like this. We wanted zero volt, whenever this voltage exceeds more than zener diode voltage. Here I am using zener diode, at op amp gain control limiter. I have connected 2 zener diode in series in reverse direction. Assume total voltage is 10V. This is zero, this is zero volt. Normal gain of op amp is R2/R1. If this is not there. When this voltage exceeds more than 10V, Current starts flowing like this. And it will not go more than 10 volt. It provide the dynamic resistance, And limit the voltage at this point. In many control application, This voltage should not go to saturation. If goes to saturation, then response becomes slow. This also protect this IC. As voltage across this will be limited to 10V. Here I have used zener diode as a voltage reference. This is comparator. What happens, When there are so many circuts, Then this supply point will have some spikes. If you connect 2 resistor here, Then spikes will pass over here also. But if we connect a zener diode, Then this point will be stable. So voltage reference will be stable, for the comparator. This resistor I have connected, such that we get the hysteresis. If we do not connect this, This hysteresis function will not be there. This is zener diode application for power supply protection. This is small resistor to limit the current. I have told in the beginning. This zener diode has short time current rating much higher than normal current. That short time rating is used here. Whenever pulse comes here, say spikes comes here. The current flows like this. It can take heavy current. And this voltage will not go more than zener diode voltage. So this R, this C, this zener diode together, provide the power supply protection. But because of this resistance, this voltage will be little lower than this. Or it will have some unregulation. If you can afford that then this circuit is very good for power supply protection. This is meter protection. I have connected one zener diode like this. When voltage across this becomes more than this, then current flows like this. But then full current will flow like this. You have to select proper rating of this zener diode, otherwise it will fail. Or we have to put another fuse or some other thing here, to limit this current. Today we will close here itself.

Why is AC motor used in the train engine

 Why is AC motor used in the train engine

 Why is AC motor used in the train engine? today topic is, why 3 phase AC motors are used, in electric train engine, now days? here, I have shown, technology improvement with time, in electric train engine, Olden days, DC motor were being used, afterwards, around year 2000 in India, 3 phase AC motor along with, GTO based control system came, and after some time, now days, 3 phase AC motor, and IGBT based control system are used, this AC motor, along with IGBT based control, are giving the advantage, olden days, this IGBT based control system, was not there. 1st advantage is, 3 phase AC motor, and IGBT based VFD/VVVF, technology provides, better speed control, and better acceleration control, in the engine, VFD means, variable frequency drive, when this control has, variable voltage also, so we call it, variable voltage variable frequency, now 2nd advantage, 3 phase AC motor, and IGBT based technology, provides unity power factor, and very less harmonics, now 3rd advantage, AC motors used in the train are, squirrel cage induction AC motor, this is easier to maintain, this kind of motor than DC motor, then there will not be, any mechanical contacts like brushes, now 4th advantage, AC motors are lighter than DC motor, for equivalent power, now 5th advantage, more effective regenerative braking, because of more effective braking, less wear and tear, of the braking system will be there, more energy saving will be there, and fast money pay back, payback is due to more saving, in the electricity bill, now I will explain, what is the payback period, pay back period, suppose money invested is Rs. 100, and after investing Rs. 100, we save Rs. 5 per month, in our electricity bill, so, to recover full Rs. 100, it will take 100/5 = 20 months, we will recover full Rs. 100 in 20 months, so this is called the pay back period, 6th advantage is, IGBT based control, with 3 phase AC induction motor, gives better performance, for a given weight and volume, 7th advantage is, AC motor in the train, with IGBT based control provides, better tractive effort, and higher adhesion level, I will try to explain these 2 points now, I have shown a train here, this is engine, this is rail, and these are wheels, when we have a CAR, there will a tyre over the wheel, and road will be rough, so, when we run the motor, or engine of the car, car will start moving, but in the train, there is no tyre over the wheel, so, it is not so easy, that we run the motor, and train start moving, I will explain you now, here, this is rail, this is wheel, gears, and motor, when motor is running, then 1st, power transfers to gears, then wheel, and a tractive force, is generate in the wheel, which try to rotate this wheel, it will not move, because for movement, rail is also required, then between wheel and rail, there will be friction, and there will be weight, like this, this together form adhesion, now this tractive force, and adhesion together, (tractive force is this), and adhesion is, in between wheel and rail, this and this together, make the train to move, here, more the utilization of friction, ( friction is between this and this), train motion will be better, in the case of the AC motor, along with IGBT based control system, utilization of the friction, is much better, here, I have given equations, and definition of adhesion variable, Adhesion variable is the ability, of the engine / locomotive, to convert the available friction, into the usable friction, at the wheel and rail interface, here, you can see 2 trains, running at the same speed, but here, wheel is moving faster than speed, so wheels are slipping here, this slip is due to, tractive effort more than adhesion level, here again, both the trains are moving, at the same speed, but 1 wheel of this train, is moving faster, so this wheel is slipping on the rail, this is due to, tractive effort more than adhesion limit, only for this wheel, in this train, both the trains are moving, with same speed, but one wheel of this train, is not moving properly, speed is less, this is sliding on the rail, this happens, if we apply the brake on the train, this is due to braking effort, is more than adhesion limit, we have to correct, the torque level here, this is tractive effort, and this is speed, this plot is tractive effort vs. speed, and this is adhesion level, this tractive effort, should be as high as possible, but should be less than adhesion limit, other wise wheel will start slipping, so, in the case of AC motor, along with IGBT based control, we can keep tractive effort, at high level, just below the adhesion limit, so utilization of tractive effort, is much more, this is slip control concept, between rail and wheel, this is time, this is torque, train speed is shown using red color, and speed is increasing with time, similarly, wheel wheel speed is shown in blue color, that also in increasing with time, wheel speed and train speed, should be equal, it is shown up to here, at this point, wheel speed, becomes more than train speed, in that case, wheel will start slipping on the rail, this difference is measured, using control system, and value of torque applied is reduced, until slip becomes zero, or speed of wheel, and train becomes equal, at that time, torque value is brought again, to normal condition, this concept of control, works better, with AC motor, and IGBT based control system, 8th advantage is, this one , I explained just now, better tractive effort, and higher adhesion level, by slip and slide control, 9th advantage is, better tractive effort, and higher adhesion level, by different power, to different axle or bogies, I will try to explain this now, during movement of the train, loading or weight distribution, is not uniform on all axles or wheels, so power or torque requirement, is different for different wheel, I have shown in this diagram, that 2 different control. and 2 different motor, are driving wheels, so depending on the requirements, we can adjust, different torque levels, for different wheels, such that wheel will not slip, this problems becomes more, when train is moving on a slope, or train is just starting, now, some big trains, will have more than 1 engine, similarly metro train, will have more than 1 engine, it is distributed in many bogies, suppose this is one engine, and this another engine, in such cases, torque and power requirement, will be different, for this engine, and this engine, then using control, we can set different torque value, here, and here, this means, power will be different, for different bogies or engine, this way, power and tractive force available, can be used more properly, in case of AC motor, along with IGBT based control system, today, we will close now, 

What is VFD & Why VFD is used in the train

  

What is VFD & Why VFD is used in the train.

  Today topic is, What is VFD & Why VFD is used in the train. VFD means varaible frequency drive. In VFD system, speed of motor is controlled by changing frequency. Now here, we have one 3 phase AC motor. This is 3 phase supply. Generally it will be induction motor. Speed of 3 phase AC motor, depends opon the frequency of AC supply. Sp speed of motor can be controlled, by changing the frequency of AC supply. Now synchronous speed of AC motor, is given by formula, Where f is the frequency of the supply. And P is the number of poles. suppose  f is 50 Hz, and P is 2. Then sysnchronous speed will be, Revolution per minute. This is synchronous speed. Actual speed will be little less, About 2 to 5 % less than this. VFD system. Here I have shown the VFD system. This consist of 4 parts. 1st is rectifier. 2nd part is DC link. 3rd part is inverter. 4th part is 3 phase AC motor. Now days, in train engine, we use 3 phase AC motor. Earlier days, DC motor were used. By now days, in latest technology, 3 phase AC motor are used. Input will be 1 phase AC. Rectifier function is, to convert single phase AC in to DC. Rectifier is made using diode also, using IGBT also. Latest technology is IGBT based. Because of IGBT based control, we can get unity power factor here. This is called the DC link. One capacitor is there. Voltage across this capacitor, may be 650 volt DC, may be 750 volt DC or may be 1800 volt. It may be anything depending upon the system. Inverter converts DC in to 3 phase AC. This also made using IGBT nowdays. Now to control the motor speed, frequency of this AC supply need to be controlled. That also is done by this inverter. This inverter does 2 jobs atleast, One is, to make 3 phase AC supply, 2nd function is to control the frequency. But in traction system, there may be so many controls. Simplest one is to control the frquency here, to control the motor speed. This is inverter. It coverts DC into 3 phase AC supply. You may be aware of 3 phase rectifier, which converts 3 phase AC into DC. But inverter is reverse type. This convert DC into AC. There are 6 switches. These are IGBT. They will be becoming ON & OFF in sequence. If this becomes ON, we get +ve voltage here. I have shown here in green color. If this becomes ON, we get negative voltage here. So these switches will be becoming ON & OFF. I have shown only 1, 2, 3, 4, 5, 6 times becoming ON & OFF. Actually these will be becoming ON & OFF many times. When you filter this green color, you get red color, which is AC. Here IGBT is ON for longer duration. So we get more voltage. Here ON period is less. So we get less voltage. So this is AC. I have shown only one phase. There will be 3 phases like this. And this is the time period, for this red color AC. Frequency will be equal to 1/T. If you want motor speed more, so we want frequency more, So we have to reduce T. So this will have to be reduced. So this inverter does 2 functions mainly. One is to generate 3 phase AC, And 2nd is to control the frequency. VFD controls. The types of controls for VFD, can be basically devided in 2 parts. One is scalar control or V/f control. 2nd is vector control. In scalar control, we keep V/f constant. V/f decides the flux. Flux we try to keep constant for better performance. Suppose we want motor speed double. We will increase the frequency to double. Then voltage also, we will make double. Suppose we want motor speed half. Then f will become half. Then V also will become half. But still speed will become half. This scalar type VFD control, are low performance type. They are simple control. And price also is low. In market, generally for small size motor, 3 phase motor, we get VFD control, those are scalar type. Because price is low. 2nd is vector control. These types are used in train engine nowdays. They have high performance. They have very omplex control. Price is also very high. And good steady & transient response. When motor speed is changing. We call it transient condition. When motor speed is steady, We call steady response. In both conditions, this vector control system will give good respose. Now benefits of VFD. First is, performance is very high. Then energy saving. VFD system consumes less electricity. In case of train & railways, electricity expenditure are very high. They want to reduce it. To reduce the electricity expenditure, They use vector type VFD. Then regenerative breaking is possible here. What is regenerative breaking ? When train is moving, It stores lot of energy because of very high mass of the train. So when we apply the break, that whole energy or part of the energy, is converted back to main power. That is called the regeneration or regenerative breaking. Means, train energy is converted, into electrical energy back to AC system. Then very good transient response. Transient means, just now I told, When speed is changing. When motor is starting, train is about to start from station, That will be transient response. So VFD control provides very good transient response. So we should feel less jerk. Very good steady respose. Steady means, constant speed. When train is running at constant speed, Then also respose of the system is very good. That, when we use vector type control. That is very complex system. High power factor. If we use IGBT based recrifier in VFD system, Then unity power factor, or about unity power factor can be achieved. Soft starting, when we start the train, that time we should start slowly, not with jerk. That is the meaning of soft starting. This is required in train, when train starts. It should not move suddenly. It should move slowly. Then torque control. We will not go in detail about torque. But as an example, when we start any vehicle, say train. Then lot of torque is required just to start. That is why, we use 1st gear during staring of the car. Because 1st gear gives more torque. So torque control is possible in VFD. That to, in vector type VFD system One more thing, I will tell about transient. That input supply will be changing. When input supply changes, that is also called transient condition. During that time, VFD system has very good transient response. Today we will close now. 

 

RCCB working principle with diagram

 

 

      Hi friends today I will explain RCCB ( Residual Current Circuit Breaker) How RCCB work and  How it’s trip work.RCCB working principle with diagram, If you like my article please share this in your group and follow my site www.automationwale.in

 

rccb working principle pdf

      Earth leakage circuit breaker function of RCCB is, when, current are not equal, it will sense and trip, the difference in current, is called residual current.

      Now, how residual current flows? here it is opening both the connections line & neutral both, here I have shown one simple system, the  secondary of the transformer, which is located in the sub-station, from there, 2 wires will come to our house, one is called line wire, one is called neutral wire, Another point is earth, the wire length may be of few Kms,     

rccb circuit diagram

      Now suppose we have connected 10 Amp load, so, current can flow line to neutral and neutral to line, it will be changing time wise,

 

    

 

      when current is flowing line to neutral, current is  10A instantaneous, if you add these two currents, total current or net current, or residual current will be zero,

      Now suppose, current is flowing FROM Neutral to line, then again summation of these currents, will be zero or residual current will be zero,    

   

single phase rccb connection diagram

     Now suppose between line and earth, we connect a load with earth, this current may be, because of insulation failure, or because of human body,

 

 

    Now Main line wire, will have main current plus earth current both, Earth current is flowing through earth, this current is not flowing in the neutral, so the current, will be more than main current, so if we add these two currents, there will be net 0.1 Amp current, that is called the residual current, because of which, circuit breaker will trip.

     Now suppose instead of resistance, there is a human body, now this person will get shock,

 

       Current will flow From body to earth, again the current will flow through line, not through the neutral, so the current will be more and we will have a difference in current or some residual current will flow, because of which, circuit breaker will trip, and it will protect us.

3 phase rccb working principle

       Now suppose, there is a fault between, neutral and ground, due to neutral insulation failure, or some other thing,

      

    Then what happens, the long neutral wire, will have some resistance, so the current, will find 2 path, so the current will be shared by neutral and earth, so again these currents will not be equal, there will be residual current and circuit breaker will trip.

        Now we will learn the concept of RCCB,

 

        This is Circuit of RCCB, this has 4 connections, L1, Neutral, L2, neutral, this is incomer And outgoing, here L1 & N to be connected to line, L2 & N are to be connected to load,

        Now what happens, when the leakage is not there, the current will be equal, the CT is inside of RCCB, so when there is no residual current and there is no earth leakage, then the current will be equal, so net primary current will be zero, no flux will flow and secondary current will be zero,

       Now suppose, we connect the resistance with earth or some human body is touching line, then the current not be equal, so there will be net current in the primary, Some current will flow in secondary also, because of that, coil will operate and RCCB will trip, it will open the switch.

       Here again I have shown a simple circuit,

 

 

       IL is line wire, IN neutral wire, R is load, because of this load, current will flow both direction, the is CT located inside the breaker, now this current, IL line current I have shown here, in graph  red color, Neutral current is shown in black color, the line current and Neutral current are equal, but in opposite directions, when we add these 2 currents, net current will be zero, Net primary current of the CT will be zero.

      Now suppose, there is a fault, or there is a leakage,

     Now the current, will flow in the line and line current will become, like Residual I , it will increase little, now when we add this line current and  neutral current, total will give some value, it will not be zero, it will be residual current, this current will behave like net current flowing in the primary of the CT, these 2 wires(IL,IN) together act like, primary turns of the CT, because of the primary current or residual current, secondary current will flow in secondary of the CT.

      The current will flow in a coil, because of the current, there will be a flux in the coil, here we have one iron piece, because of this flux, this will attract  mechanically and the switch is connected mechanically, so the contact will open, but this will happen, when there is a residual current, when this is not there, both currents are equal, no primary current, no secondary current, no breaker trip operation, breaker will operate only, when net residual current flows.

 Types of RCCB,

    Now, Types of RCCB,

    Mainly there are 3 types,

1)     1) AC

2)     2) A

3)     3)B

        AC types of RCCB, is sensitive for AC currents,

        A type is sensitive for AC current + pulse current, this is pulse type current, it will be there, when there is a rectifier or inverter or some thyristor is connected, A type RCCB for AC and pulse both.

       B type RCCB, is sensitive for AC , as well as pure DC, In our home, generally AC types are used, But in lab or where inverter is there or converters or thyristors are there, it is possible that, output of the rectifier is getting short circuited with earth, that time we have to use B type RCCB.

rccb 30ma or 100ma

       Now poles, RCCB may be available, with many types of poles, for single phase line and neutral, there will be 2 poles.

      For 3 phases, there will be 4 wires, a, b,  c and neutral, so we require 4 contacts, that is called the 4 pole, similarly trip current rating may be, 30mA, 100mA, 300 mA or some other value, this means, whenever residual current, becomes more than 30mA, Then RCCB will trip.

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  What is Impedance, Resistance difference, Series RLC circuit

      Hi friends Today I will explain, What is the difference between resistance, reactance and impedance.if you like my article,please share in your facebook,whatsapp,instagram groups and follow my site.so,let's start.

  

what is impedance,difference between resistance and impedance,impedance,capacitor impedance,reactance,series rlc circuit,impedance resistance difference,difference between reactance and impedance,impedance of series rlc circuit,resistance reactance and impedance,reactance and impedance,resistance impedance difference,what is reactance,inductance

what is impedance

        This is simple AC circuit. This is AC supply. Voltage is V. VR is resistor and VL is inductor And I is the current flowing in the circuit. This I current will flow in VL  and VR  also. Same current.

        Now,  voltage across the resistor is VR, Voltage across this inductor is VL. Resistance of resistor is R. Similarly, inductance of inductor is L And inductive reactance will be equal to ωL. So inductor has 2 values, one is inductance L, Another is inductive reactance  ωL.  Then impedance will be total from VR To VL  And will be equal to. The formula is given above. Here I have written  ωL and  Lω also. Both are same. So value of impedance depends upon R, L, ω. Where omega is equal to 2 π f. f is the frequency of the AC supply.

       Now suppose value of R=0. Then Resistance is 0 & it's look like short. Now when R becomes zero,so,formula becomes like this. Only Lω  will be remaining.  So when R = 0. So in this type of circuit, Impedance & inductive reactance both will be equal and will be equal to Lω. 

impedance resistance difference

       Now suppose instead of R, L=0. When L become zero, ωL also becomes zero And VL will look like short. When this becomes short, There will not be any Lω . Because  L value is zero. So impedance will be equal to R,The square will be cancelled out with square root. That is equal to resistance. So, when R & L both are there and value of L is zero Or you can say, there is no L. Then impedance & resistance will be equal. and it will be R. 

      Now to calculate the value of R resistance using ohms (R=Vr/I) law we divide V by R. Here we take the voltage across the resistor. which is VR. So the voltage, devided by the current, because current is same every where, will be equal to resistance.

      Similarly here, (ωL=VL/I) to get the inductive reactance, we take the voltage VL, which is across inductor. So voltage across inductor VL / current I, is equal to ωL. Inductive reactance.        To calculate the impedance, We take full voltage, So this full voltage (V/I= impedance).

capacitor impedance

       I have shown C capacitor in place of inductor. So capacitor is the name of VC. It has 2 values.

resistance reactance and impedance

          One is capacitance= C And another is capacitive reactance= 1/ Cω. there is one resistor. So resistance is R. And capacitive reactanc is 1/Cω. And

       Impedance (Z) will be full, Impedance is depending upon R, C, ω  all three. 

       Now suppose here, R = 0. So, The square & the under root will be cancelled out. so remaining value will be 1/Cω, That is nothing but Capacitive reactance. So impedance & capacitive reactance , will be same &  will be equal to 1/Cω.when in RC circuit, value of R become zero. 

       Now suppose  capacitive reactance 1/Cω=0.  C should be infinite. So, C is equal to infinite. In this case, when capacitive reactance is zero, VC will show like short. because reactance value is zero. So impedance will be equal to square root R square. Root & square root will cancel, only R is remaining. So, in R & C case, If value of capacitive reactance is zero, then impedance & resistance becomes equal And will be equal to R. 

       Now here suppose we add one inductor also. Then  formula will be change

       value of impedance will change. Where the reactance of inductor. Suppose the reactance and the reactance becomes equal, then they will cancel out. This is called the resonance And value of impedance will be equal to only R  And the square & square root will cancel out. 

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