Understanding Arc Production in Circuit Breakers

Hi all, today we are going to discuss about the phenomenon of production of the arc in a circuit breaker. So the arc consists of a column of ionized gas having the molecules which have lost one or more electrons. Because of that it comes. Let us take for example there is some ion that is generated. Ion means it has lost some electrons from the atom. So that we call as the ion because whenever any atom or any molecule loses some electrons so it will become positively charged. So it is positively charged and there are some free electrons also. So generally the weight of the free electrons are very less when compared to the weight of the ion because ion weight will be nearly equal to the weight of your atom because the weight of the electron is very less. It has lost few electrons from it. so this electron will be attracted towards the positive terminal and your ion or positive ion will be attracted towards the negative terminal so as the weight of this positive charge is more so it will accelerate at a lesser velocity so because of this the velocity of this one will be very less because the weight is very high for a given potential difference between these two terminals or for a given electric field that is applied on this because there is a terminal positive there is a negative terminal electric field is produced between them so for this field this will accelerate at a lower velocity because of the weight whereas if you go for the electron because the weight of the electron is very less so automatically the velocity of this electron will be very high so it will accelerate at a very faster rate so in the process of moving from this negative terminal towards the positive terminal so it will collide with the neighboring so many atoms or the molecules So whenever this electron come and hit these molecules, so automatically it will dislodge some more electrons in that process because of the collision process. Getting it? So in that way, the number of carriers will go on increasing and that is a cumulative process. So what I mean to tell, the effect of the current produced due to the positive ions is very less compared to the current that can be produced using the negative charges or because of the electrons that are liberated out. So that's why we mainly concern about the negative charges only the negative charge that is passing from cathode towards anode So the same thing I have just represented here the positive ions are attracted towards the negative contact that is cathode But as they comprise almost the entire weight of the atom They move at a relatively less speed and hence they does not contribute for the passes of current they contribute But the percentage will be very less. So the electrons being negatively charged and are attracted towards the positive contact that is anode with high velocity because the weight is less and on the way they will detach more electrons due to the collision so how these negative charges produced so we have conclude from here that negative charge is the major thing that is responsible for the production of the arc or maintaining the arc between the contacts because in the form of the arc only the current is passing between the contacts so you can see as soon as the contacts are separated so how the arc will be produced so this is based on two theories one is by high voltage gradient at the cathode resulting into field emission let us assume this is my positive terminal this is my negative terminal or we can call as the cathode and this terminal is anode so first thing we have to remember that most of the cases we go for the copper material is used for the case of contacts because of its good conductivity and it can withstand the more temperature also easily when compared to aluminum. So now where our concern is only about the case of the copper. So let us discuss the basics and then we will proceed for the conclusions. So first one by high voltage gradient at the cathode. So as a moving contact is withdrawn so what happens the contact area gets decreased through which the current can pass because current cannot change suddenly because of the inductance and the capacitance. that means energy storage elements that are available in your circuit the current cannot be suddenly brought to zero so because of this the current will try to pass through this intermediate medium so how it will passes whenever the moving contact is withdrawn the contact area and pressure decreases so the current whatever is there that is that should pass through the air So automatically, because it should pass through a less area and through the air, so automatically resistance for the passage of current increases. But generally, this resistance will be very less in the order of one ohm only. It will be less than one ohm. But as we know that huge value of current is passing through a very small area. So automatically, the current density increases. That means the amount of current passing per unit area that will be very high. This will be in the order of... 10 to the power of 6 amperes per centimeter square. So because of this huge value of the current gradient so automatically high potential drop or high voltage drop happens at these contacts because resistance let us take as 1 ohm and the current density is 10 to the power of 6 amperes per centimeter square if you multiply this you will get it of the order of 10 to the power of 6 volts per centimeter if you are taking as 1 ohm for example we know that the breakdown strength of air is only 30 kV per centimeter as this magnitude is greater than that much automatically it leads to breakdown of the material in between or the breakdown of the dielectric material in between and that leads to dislodging of the electrons from the material in between and the same thing the cathode material whichever is there because at this contact surface Because it is having the high value of the voltage gradient so the charges will be dislodged from the cathode surface also So this is the first phenomena and the second phenomenon is by increase of the temperature resulting into thermo ionic emissions so what happens whenever the temperature is increased the molecules will start vibrating and they will absorb that heat energy and if the energy absorbed is so much high and that may lead to the vibration or the vibrating electrons will come out of the attraction force of the nucleus and they may get liberated from your atom completely and the free electrons will be generated so that is called as a thermo ionic emission so to explain this as the contacts are separated so contact area will decrease so as the contact area decreases so the current density is increased so automatically the temperature is increased so that leads to thermal emissions so because of the heat also the emissions happens from this but i have told you that already the contacts of the circuit breaker are made up of the copper so the thermo ionic emission is quite low from the copper this dermoionic emission can come from your material that means the surrounding material that is used which gas is there in between but it cannot be generated by the copper or it cannot generate from the cathode so only the option that can be possible is by the process of field emission so that means what happens whenever the contacts are separated out due to the field emission some electrons are generated And when the electrons are passing towards the positive charge because of the attraction force, they will dislodge some more electrons in the process and increase the heat of the medium. So whenever the heat is increased, so automatically that leads to dislodging more things. So let us proceed for the same thing. How the maintenance of the arc is done? We have seen how the electrons are generated when the contacts are separated out. So now how the arc is maintained because of the electrons that are generated? So when the electrons moves from cathode to the anode at high velocity, they collide with the atoms and the molecules with the gases and the vapors existing between them and dislodge more electrons. So this ionization process also increases due to some other phenomena. There with the increase in the temperature, automatically the kinetic energy gained by the electron also increases as well as the vibration of the molecules which are in between also increases. Thank you. because of the molecular vibrations the collisions increases because the collision of the electron with them increases as more collisions are there so more carriers will be generated this is the first one and the second one is if the field strength or voltage gradient between the terminals is increased so that means for the case of high voltage so automatically the velocity of electron depends on the potential gradient as the potential gradient is increased or the electric field is increased so automatically velocity of electron increases so the collision increases in that case also more carriers are generated so i am just summarizing up to here first thing is we have summarized here up to now that whenever the contacts are separated so if you are taking two contacts whenever these two contacts are separated so now the electrons are liberated from the cathode so the electrons are liberated from the cathode once the electrons are liberated from the cathode when they move from cathode towards the anode in that process they will dislodge or generate so many extra carriers because of collision with the gas in between and whenever this collision happens because of that the heat is also produced so this is a cumulative action so the heat goes on increasing and automatically the number of carriers will goes on increasing and this heat produced may go to extreme high value and may lead to damage your circuit breaker. So you have to take care that this temperature is not gone to extreme high value. So now practically it is observed that so if you are taking this as anode, this is your cathode, there is an arc established between the contacts. So let us assume that Eb is the voltage drop across the contacts which is called as the arc voltage. It is a voltage drop across the arc is known as the arc voltage. So how the arc voltage will respond? So they have experimentally tested in the laboratory and they have found that at the time of the current zero, the voltage drop or voltage across the arc will be extremely high. This is the curve that is followed as the current is increasing because we know that most of our supplies are AC only because we are going with the AC. The current start from zero goes to peak again decreases, go to negative and come back to zero. So this way, with respect to the time, your current will go on changing. Agree with me? So that's why at the current zero the voltage will be maximum and as the current is increasing it is observed that the voltage decreases to a very less value then it is maintained to that less value. It will reach up to EZ and it will come back or come down to EL and EL is maintained and as the current is increased you can see here as the current reaches the peak it is maintained at this voltage or at this voltage. So automatically when the current is decreasing now going in the opposite direction. that means when the current is going like this so the voltage is maintained up to certain level after that suddenly when the current is near to zero voltage becomes negative again maximum again the same procedure same type of curve will be followed so based on this we can calculate how much amount of the heat is produced actually for the analysis of this the concept of the plasma how the plasma responds so that is required which is very tedious so that's why generally we depend on the empirical formulas that are suggested by different scientists only for the analysis of this one because that will be easy. So, this arc energy also they have given the formula that arc energy or the heat that is produced will be equal to integration from 0 to T arc. It is the time duration for which the arc exists. So, instantaneous value of the current multiplied by E b is the instantaneous value of the voltage of this arc multiplied by d t. because integration of I into V into dt that gives my energy we know. So this will go on producing the heat. So this heat will goes on increasing and if you want to see the curve between the voltage and the current the curve between the voltage and current will be like this. So that whatever explained there same thing I am telling when the current is equal to 0 voltage is equal to maximum. So it will reach some minimum value there it is mentioned as VL and the higher value let us take as V max V minimum value. So it will reach the minimum value at the again current 0 when current is going to negative suddenly it will reach the negative maximum again decrease. So as the contacts are separated apart then how the characteristics are going to change. So that is given by a scientist called as Ayrton's equation. This scientist Ayrton has proposed this equation. He tells that the EMF that is dropping across the contacts can be written as EB is equal to A plus B by IA where the value of A is equal to alpha plus gamma L where for the case of copper electrodes because we know we are going for the copper. So for the copper this alpha is equal to 30 volts and the value of gamma will be equal to 10 volts per centimeter and similarly that B is given by beta plus delta L where beta is 10 volt amperes and delta is equal to 30 volt amperes per centimeter and L is the arc length in centimeters. The length of the arc in centimeters that means gap between the electrodes or the path the total length by which your arc is passing and you can see divided by ia ia is the instantaneous value of the arc current current passing through your arc getting this one and If you are plotting the curve, you are getting the plot like this. And now what happens, the voltage across the arc will be in phase with the arc current because whenever the arc is produced, that majority of the energy is dissipated in the form of heat. We know that whichever the active energy is there, that we represent as equivalent to resistance. or we can tell that whichever is the active energy so in that case active energy means the voltage and current will be in phase with each other so that is the main reason the arc current is predominantly resistive that means whatever the arc current is produced that is dissipated in the form of a heat only majority value so we can take it as approximately equal to resistive and as the time is passing because the distance between the contacts is goes on increasing because we are separating the contacts and there is one fixed contact and moving contact will goes on moving because they are separating so automatically the distance between the contacts will goes on increasing so as the distance between the contact goes on increasing so automatically the arc resistance increases because the length by which this arc should pass will automatically increase when the length is increased the arc resistance increases so automatically the arc voltage will increase that means with change in the cycles with respect to the time the arc voltage will goes on increasing this is what i have represented here i hope this is clear up to now so let us proceed further so it is observed that the conductance of the arc is directly proportional to how many number of ionized electrons are there per centimeter cube which we can call as the charge density ionized charge density how much value of ionized charges are there per centimeter cube that means more the value of ionized particles or the density of the ionized particles more will be the conductance of the arc so more time your arc will continue so if the arc is continuing for more time the integration term is increasing so automatically more heat is produced that may lead to explosion or bursting of your circuit breaker or damage your circuit breaker and it is also observed that the conductance of the arc is proportional to diameter of the arc and is inversely proportional to length of the arc that means if the arc length that means the length by which your arc should pass is increased then in that case the conductance decreases automatically the current decreases and when the current is decreased automatically heat will be decreased so it will be safe and second one as the diameter is decreased in that case also conductance decreases so in that case also we can extinguish your arc so we can tell that if you want to extinguish the arc either decrease the diameter of the arc or increase the length of the arc or decrease the number of ionized particles per centimeter cube. That means whichever the ionized particles are there in the medium, so remove those ionized particles. So how we can remove the ionized particles? We can remove the ionized particles by cooling. So whenever you decrease the temperature, automatically the recombination happens and the electrons will again recombine with your atoms and they will go to their stable state. So automatically the number of ionized carriers will decrease. So this can be done by cooling. Or second option is remove whatever carriers are generated, remove them using some procedure so that carriers will be removed from there. Let us take for example using SF6 gas. What it will do? It will absorb the negative ions. So automatically as it absorbs the electrons, so automatically. the number of carriers are decreased so in that way we can extinguish the arc or other option is remove the carriers by using by blowing some air through the contact material so using that also we can do so different techniques are employed for removing the ionized particles from there and along with that to decrease the diameter of the arc what we do the contacts when they are separating that the area will be very less and they can pass through only the narrow channel using that the diameter can be decreased and the length of the arc can be increased by using the splitting of the arc. So how this is done, this also we are going to see in the coming sections. I hope how the arc is generated, so how the heat is produced, and how to decrease the effect of the arc is clear to you. So in the next class, we are going to see what is the procedure for extinguishing the arc by following these procedures. What are the different theorems that are available out of that which are used in practice. So this one we are going to discuss in our next class. I hope everything is clear up to now. 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.

So that we call as the ion because whenever any atom or any molecule loses some electrons so it will become positively charged. So it is positively charged and there are some free electrons also. So generally the weight of the free electrons are very less when compared to the weight of the ion because ion weight will be nearly equal to the weight of your atom because the weight of the electron is very less.

It has lost few electrons from it. so this electron will be attracted towards the positive terminal and your ion or positive ion will be attracted towards the negative terminal so as the weight of this positive charge is more so it will accelerate at a lesser velocity so because of this the velocity of this one will be very less because the weight is very high for a given potential difference between these two terminals or for a given electric field that is applied on this because there is a terminal positive there is a negative terminal electric field is produced between them so for this field this will accelerate at a lower velocity because of the weight whereas if you go for the electron because the weight of the electron is very less so automatically the velocity of this electron will be very high so it will accelerate at a very faster rate so in the process of moving from this negative terminal towards the positive terminal so it will collide with the neighboring so many atoms or the molecules So whenever this electron come and hit these molecules, so automatically it will dislodge some more electrons in that process because of the collision process. Getting it?

So in that way, the number of carriers will go on increasing and that is a cumulative process. So what I mean to tell, the effect of the current produced due to the positive ions is very less compared to the current that can be produced using the negative charges or because of the electrons that are liberated out. So that's why we mainly concern about the negative charges only the negative charge that is passing from cathode towards anode So the same thing I have just represented here the positive ions are attracted towards the negative contact that is cathode But as they comprise almost the entire weight of the atom They move at a relatively less speed and hence they does not contribute for the passes of current they contribute But the percentage will be very less.

So the electrons being negatively charged and are attracted towards the positive contact that is anode with high velocity because the weight is less and on the way they will detach more electrons due to the collision so how these negative charges produced so we have conclude from here that negative charge is the major thing that is responsible for the production of the arc or maintaining the arc between the contacts because in the form of the arc only the current is passing between the contacts so you can see as soon as the contacts are separated so how the arc will be produced so this is based on two theories one is by high voltage gradient at the cathode resulting into field emission let us assume this is my positive terminal this is my negative terminal or we can call as the cathode and this terminal is anode so first thing we have to remember that most of the cases we go for the copper material is used for the case of contacts because of its good conductivity and it can withstand the more temperature also easily when compared to aluminum. So now where our concern is only about the case of the copper. So let us discuss the basics and then we will proceed for the conclusions. So first one by high voltage gradient at the cathode. So as a moving contact is withdrawn so what happens the contact area gets decreased through which the current can pass because current cannot change suddenly because of the inductance and the capacitance.

that means energy storage elements that are available in your circuit the current cannot be suddenly brought to zero so because of this the current will try to pass through this intermediate medium so how it will passes whenever the moving contact is withdrawn the contact area and pressure decreases so the current whatever is there that is that should pass through the air So automatically, because it should pass through a less area and through the air, so automatically resistance for the passage of current increases. But generally, this resistance will be very less in the order of one ohm only. It will be less than one ohm. But as we know that huge value of current is passing through a very small area.

So automatically, the current density increases. That means the amount of current passing per unit area that will be very high. This will be in the order of... 10 to the power of 6 amperes per centimeter square. So because of this huge value of the current gradient so automatically high potential drop or high voltage drop happens at these contacts because resistance let us take as 1 ohm and the current density is 10 to the power of 6 amperes per centimeter square if you multiply this you will get it of the order of 10 to the power of 6 volts per centimeter if you are taking as 1 ohm for example we know that the breakdown strength of air is only 30 kV per centimeter as this magnitude is greater than that much automatically it leads to breakdown of the material in between or the breakdown of the dielectric material in between and that leads to dislodging of the electrons from the material in between and the same thing the cathode material whichever is there because at this contact surface Because it is having the high value of the voltage gradient so the charges will be dislodged from the cathode surface also So this is the first phenomena and the second phenomenon is by increase of the temperature resulting into thermo ionic emissions so what happens whenever the temperature is increased the molecules will start vibrating and they will absorb that heat energy and if the energy absorbed is so much high and that may lead to the vibration or the vibrating electrons will come out of the attraction force of the nucleus and they may get liberated from your atom completely and the free electrons will be generated so that is called as a thermo ionic emission so to explain this as the contacts are separated so contact area will decrease so as the contact area decreases so the current density is increased so automatically the temperature is increased so that leads to thermal emissions so because of the heat also the emissions happens from this but i have told you that already the contacts of the circuit breaker are made up of the copper so the thermo ionic emission is quite low from the copper this dermoionic emission can come from your material that means the surrounding material that is used which gas is there in between but it cannot be generated by the copper or it cannot generate from the cathode so only the option that can be possible is by the process of field emission so that means what happens whenever the contacts are separated out due to the field emission some electrons are generated And when the electrons are passing towards the positive charge because of the attraction force, they will dislodge some more electrons in the process and increase the heat of the medium.

So whenever the heat is increased, so automatically that leads to dislodging more things. So let us proceed for the same thing. How the maintenance of the arc is done?

We have seen how the electrons are generated when the contacts are separated out. So now how the arc is maintained because of the electrons that are generated? So when the electrons moves from cathode to the anode at high velocity, they collide with the atoms and the molecules with the gases and the vapors existing between them and dislodge more electrons.

So this ionization process also increases due to some other phenomena. There with the increase in the temperature, automatically the kinetic energy gained by the electron also increases as well as the vibration of the molecules which are in between also increases. Thank you.

because of the molecular vibrations the collisions increases because the collision of the electron with them increases as more collisions are there so more carriers will be generated this is the first one and the second one is if the field strength or voltage gradient between the terminals is increased so that means for the case of high voltage so automatically the velocity of electron depends on the potential gradient as the potential gradient is increased or the electric field is increased so automatically velocity of electron increases so the collision increases in that case also more carriers are generated so i am just summarizing up to here first thing is we have summarized here up to now that whenever the contacts are separated so if you are taking two contacts whenever these two contacts are separated so now the electrons are liberated from the cathode so the electrons are liberated from the cathode once the electrons are liberated from the cathode when they move from cathode towards the anode in that process they will dislodge or generate so many extra carriers because of collision with the gas in between and whenever this collision happens because of that the heat is also produced so this is a cumulative action so the heat goes on increasing and automatically the number of carriers will goes on increasing and this heat produced may go to extreme high value and may lead to damage your circuit breaker. So you have to take care that this temperature is not gone to extreme high value. So now practically it is observed that so if you are taking this as anode, this is your cathode, there is an arc established between the contacts.

So let us assume that Eb is the voltage drop across the contacts which is called as the arc voltage. It is a voltage drop across the arc is known as the arc voltage. So how the arc voltage will respond?

So they have experimentally tested in the laboratory and they have found that at the time of the current zero, the voltage drop or voltage across the arc will be extremely high. This is the curve that is followed as the current is increasing because we know that most of our supplies are AC only because we are going with the AC. The current start from zero goes to peak again decreases, go to negative and come back to zero.

So this way, with respect to the time, your current will go on changing. Agree with me? So that's why at the current zero the voltage will be maximum and as the current is increasing it is observed that the voltage decreases to a very less value then it is maintained to that less value. It will reach up to EZ and it will come back or come down to EL and EL is maintained and as the current is increased you can see here as the current reaches the peak it is maintained at this voltage or at this voltage.

So automatically when the current is decreasing now going in the opposite direction. that means when the current is going like this so the voltage is maintained up to certain level after that suddenly when the current is near to zero voltage becomes negative again maximum again the same procedure same type of curve will be followed so based on this we can calculate how much amount of the heat is produced actually for the analysis of this the concept of the plasma how the plasma responds so that is required which is very tedious so that's why generally we depend on the empirical formulas that are suggested by different scientists only for the analysis of this one because that will be easy. So, this arc energy also they have given the formula that arc energy or the heat that is produced will be equal to integration from 0 to T arc. It is the time duration for which the arc exists.

So, instantaneous value of the current multiplied by E b is the instantaneous value of the voltage of this arc multiplied by d t. because integration of I into V into dt that gives my energy we know. So this will go on producing the heat. So this heat will goes on increasing and if you want to see the curve between the voltage and the current the curve between the voltage and current will be like this. So that whatever explained there same thing I am telling when the current is equal to 0 voltage is equal to maximum.

So it will reach some minimum value there it is mentioned as VL and the higher value let us take as V max V minimum value. So it will reach the minimum value at the again current 0 when current is going to negative suddenly it will reach the negative maximum again decrease. So as the contacts are separated apart then how the characteristics are going to change.

So that is given by a scientist called as Ayrton's equation. This scientist Ayrton has proposed this equation. He tells that the EMF that is dropping across the contacts can be written as EB is equal to A plus B by IA where the value of A is equal to alpha plus gamma L where for the case of copper electrodes because we know we are going for the copper. So for the copper this alpha is equal to 30 volts and the value of gamma will be equal to 10 volts per centimeter and similarly that B is given by beta plus delta L where beta is 10 volt amperes and delta is equal to 30 volt amperes per centimeter and L is the arc length in centimeters.

The length of the arc in centimeters that means gap between the electrodes or the path the total length by which your arc is passing and you can see divided by ia ia is the instantaneous value of the arc current current passing through your arc getting this one and If you are plotting the curve, you are getting the plot like this. And now what happens, the voltage across the arc will be in phase with the arc current because whenever the arc is produced, that majority of the energy is dissipated in the form of heat. We know that whichever the active energy is there, that we represent as equivalent to resistance. or we can tell that whichever is the active energy so in that case active energy means the voltage and current will be in phase with each other so that is the main reason the arc current is predominantly resistive that means whatever the arc current is produced that is dissipated in the form of a heat only majority value so we can take it as approximately equal to resistive and as the time is passing because the distance between the contacts is goes on increasing because we are separating the contacts and there is one fixed contact and moving contact will goes on moving because they are separating so automatically the distance between the contacts will goes on increasing so as the distance between the contact goes on increasing so automatically the arc resistance increases because the length by which this arc should pass will automatically increase when the length is increased the arc resistance increases so automatically the arc voltage will increase that means with change in the cycles with respect to the time the arc voltage will goes on increasing this is what i have represented here i hope this is clear up to now so let us proceed further so it is observed that the conductance of the arc is directly proportional to how many number of ionized electrons are there per centimeter cube which we can call as the charge density ionized charge density how much value of ionized charges are there per centimeter cube that means more the value of ionized particles or the density of the ionized particles more will be the conductance of the arc so more time your arc will continue so if the arc is continuing for more time the integration term is increasing so automatically more heat is produced that may lead to explosion or bursting of your circuit breaker or damage your circuit breaker and it is also observed that the conductance of the arc is proportional to diameter of the arc and is inversely proportional to length of the arc that means if the arc length that means the length by which your arc should pass is increased then in that case the conductance decreases automatically the current decreases and when the current is decreased automatically heat will be decreased so it will be safe and second one as the diameter is decreased in that case also conductance decreases so in that case also we can extinguish your arc so we can tell that if you want to extinguish the arc either decrease the diameter of the arc or increase the length of the arc or decrease the number of ionized particles per centimeter cube.

That means whichever the ionized particles are there in the medium, so remove those ionized particles. So how we can remove the ionized particles? We can remove the ionized particles by cooling.

So whenever you decrease the temperature, automatically the recombination happens and the electrons will again recombine with your atoms and they will go to their stable state. So automatically the number of ionized carriers will decrease. So this can be done by cooling. Or second option is remove whatever carriers are generated, remove them using some procedure so that carriers will be removed from there.

Let us take for example using SF6 gas. What it will do? It will absorb the negative ions. So automatically as it absorbs the electrons, so automatically. the number of carriers are decreased so in that way we can extinguish the arc or other option is remove the carriers by using by blowing some air through the contact material so using that also we can do so different techniques are employed for removing the ionized particles from there and along with that to decrease the diameter of the arc what we do the contacts when they are separating that the area will be very less and they can pass through only the narrow channel using that the diameter can be decreased and the length of the arc can be increased by using the splitting of the arc.

So how this is done, this also we are going to see in the coming sections. I hope how the arc is generated, so how the heat is produced, and how to decrease the effect of the arc is clear to you. So in the next class, we are going to see what is the procedure for extinguishing the arc by following these procedures.

What are the different theorems that are available out of that which are used in practice. So this one we are going to discuss in our next class. I hope everything is clear up to now. 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.

Transcript for:Understanding Arc Production in Circuit Breakers

Transcript for:
Understanding Arc Production in Circuit Breakers