Drift Velocity?
If a particle moves in space in such a manner that it randomly changes its directions and velocities, the resultant of these random motions as a whole is called drift velocity.
The definition of drift velocity can be understood by imagining the random motion of free electrons in a conductor. The free electrons move in a conductor with random velocities and random directions. When we apply an electric field across the conductor, the randomly moving electrons experience an electrical force in the direction of the field.
Due to this field, the electrons do not give up their randomness of motion, but they will shift towards higher potential with their random motion. That means the electrons will drift towards higher potential along with their random motions. Thus, every electron will have a net velocity towards the higher potential end of the conductor, and we refer this net velocity as the drift velocity of electrons. Hopping, you understand the definition of drift velocity. The current due to this drift movement of electrons inside an electrically stressed conductor, is known as drift current. It is needless to say that every electric current is "drift current".
If a particle moves in space in such a manner that it randomly changes its directions and velocities, the resultant of these random motions as a whole is called drift velocity.
The definition of drift velocity can be understood by imagining the random motion of free electrons in a conductor. The free electrons move in a conductor with random velocities and random directions. When we apply an electric field across the conductor, the randomly moving electrons experience an electrical force in the direction of the field.
Due to this field, the electrons do not give up their randomness of motion, but they will shift towards higher potential with their random motion. That means the electrons will drift towards higher potential along with their random motions. Thus, every electron will have a net velocity towards the higher potential end of the conductor, and we refer this net velocity as the drift velocity of electrons. Hopping, you understand the definition of drift velocity. The current due to this drift movement of electrons inside an electrically stressed conductor, is known as drift current. It is needless to say that every electric current is "drift current".
Superconductivity :
The pairing of electrons in certain materials when cooled below a critical temperature, causing the material to lose all resistance to electricity flow. Superconductors can carry electric current without any energy losses.
The pairing of electrons in certain materials when cooled below a critical temperature, causing the material to lose all resistance to electricity flow. Superconductors can carry electric current without any energy losses.
Conduction band; Conduction level :
Energy level at which electrons are not bound to (orbiting) a specific atomic nucleus but are free to wander among the atoms. An energy band in which electrons can move freely in a solid, producing a net transport of charge.
Energy level at which electrons are not bound to (orbiting) a specific atomic nucleus but are free to wander among the atoms. An energy band in which electrons can move freely in a solid, producing a net transport of charge.
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Valence band :
The highest energy band in a semiconductor that can be filled with electrons.
The highest energy band in a semiconductor that can be filled with electrons.
Band gap :
In a semiconductor, the energy difference between the highest valence band and the lowest conduction band.
In a semiconductor, the energy difference between the highest valence band and the lowest conduction band.
Solenoid :
A coil of wire wound uniformly on a cylindrical former, having a length which is large compared with its radius.
A coil of wire wound uniformly on a cylindrical former, having a length which is large compared with its radius.
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SRAM :
Static RAM. A RAM that stores information in flip flop cells which do not have to be refreshed unlike those of the DRAM.
Static RAM. A RAM that stores information in flip flop cells which do not have to be refreshed unlike those of the DRAM.
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super-conductivity :
The electrical resistance of a metal or alloy which decreases with decrease in temperature and becoming vanishingly small at a finite temperature.
The electrical resistance of a metal or alloy which decreases with decrease in temperature and becoming vanishingly small at a finite temperature.
What is Control System?
In a System the output and inputs are interrelated in such a manner that the output quantity or variable is controlled by input quantity, then such a system is called Control System.
The output quantity is called controlled variable or response and the input quantity is called command signal or excitation.
In a System the output and inputs are interrelated in such a manner that the output quantity or variable is controlled by input quantity, then such a system is called Control System.
The output quantity is called controlled variable or response and the input quantity is called command signal or excitation.
What are different types of Control Systems?
Two major types of Control Systems are 1) Open loop Control System
2) Closed Loop Control Systems
Open loop Control Systems: The Open loop Control System is one in which the Output Quantity has no effect on the Input Quantity. No feedback is present from the output quantity to the input quantity for correction.
Closed Loop Control System: The Closed loop Control System is one in which the feedback is provided from the Output quantity to the input quantity for the correction so as to maintain the desired output of the system.
Two major types of Control Systems are 1) Open loop Control System
2) Closed Loop Control Systems
Open loop Control Systems: The Open loop Control System is one in which the Output Quantity has no effect on the Input Quantity. No feedback is present from the output quantity to the input quantity for correction.
Closed Loop Control System: The Closed loop Control System is one in which the feedback is provided from the Output quantity to the input quantity for the correction so as to maintain the desired output of the system.
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What is a feedback in Control System?
The Feedback in Control System in one in which the output is sampled and proportional signal is fed back to the input for automatic correction of the error ( any change in desired output) for futher processing to get back the desired output.
The Feedback in Control System in one in which the output is sampled and proportional signal is fed back to the input for automatic correction of the error ( any change in desired output) for futher processing to get back the desired output.
Why Negative Feedback is preffered in the Control System?
The role of Feedback in control system is to take the sampled output back to the input and compare output signal with input signal for error ( deviation from the desired result).
Negative Feedback results in the better stability of the system and rejects any disturbance signals and is less sensitive to the parameter variations. Hence in control systems negative feedback is considered.
The role of Feedback in control system is to take the sampled output back to the input and compare output signal with input signal for error ( deviation from the desired result).
Negative Feedback results in the better stability of the system and rejects any disturbance signals and is less sensitive to the parameter variations. Hence in control systems negative feedback is considered.
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What is the effect of positive feedback on stability of the system?
Positive feedback is not used generally in the control system because it increases the error signal and drives the system to instability. But positive feedbacks are used in minor loop control systems to amplify certain internal signals and parameters.
Positive feedback is not used generally in the control system because it increases the error signal and drives the system to instability. But positive feedbacks are used in minor loop control systems to amplify certain internal signals and parameters.
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What is Latching current?
Gate signal is to be applied to the thyristor to trigger the thyristor ON in safe mode. When the thyristor starts conducting the forward current above the minimum value, called Latching current, the gate signal which is applied to trigger the device in no longer require to keep the scr in ON position.
Gate signal is to be applied to the thyristor to trigger the thyristor ON in safe mode. When the thyristor starts conducting the forward current above the minimum value, called Latching current, the gate signal which is applied to trigger the device in no longer require to keep the scr in ON position.
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What is Holding current ?
When scr is conducting current in forward conduction state, scr will return to forward blocking state when the anode current or forward current falls below a low level called Holding current
Note: Latching current and Holding current are not same. Latching current is associated with the turn on process of the scr whereas holding current is associated with the turn off process. In general holding current will be slightly lesser than the latching current.
When scr is conducting current in forward conduction state, scr will return to forward blocking state when the anode current or forward current falls below a low level called Holding current
Note: Latching current and Holding current are not same. Latching current is associated with the turn on process of the scr whereas holding current is associated with the turn off process. In general holding current will be slightly lesser than the latching current.
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Why thyristor is considered as Charge controlled device?
During the triggering process of the thyristor from forward blocking state to forward conduction state through the gate signal, by applying the gate signal (voltage between gate and cathode) increases the minority carrier density in the p-layer and thereby facilitate the reverse break over of the junction J2 and thyristor starts conducting. Higher the magnitude of the gate current pulse, lesser is the time required to inject the charge and turning on the scr. By controlling the amount of charge we can control the turning on time of the scr.
During the triggering process of the thyristor from forward blocking state to forward conduction state through the gate signal, by applying the gate signal (voltage between gate and cathode) increases the minority carrier density in the p-layer and thereby facilitate the reverse break over of the junction J2 and thyristor starts conducting. Higher the magnitude of the gate current pulse, lesser is the time required to inject the charge and turning on the scr. By controlling the amount of charge we can control the turning on time of the scr.
What are the different losses that occur in thyristor while operating?
Different losses that occur are
a)Forward conduction losses during conduction of the thyristor
b)Loss due to leakage current during forward and reverse blocking.
c)Power loss at gate or Gate triggering loss.
d)Switching losses at turn-on and turn-off.
Different losses that occur are
a)Forward conduction losses during conduction of the thyristor
b)Loss due to leakage current during forward and reverse blocking.
c)Power loss at gate or Gate triggering loss.
d)Switching losses at turn-on and turn-off.
What is meant by knee point voltage?
Knee point voltage is calculated for electrical Current transformers and is very important factor to choose a CT. It is the voltage at which a CT gets saturated.(CT-current transformer).
Knee point voltage is calculated for electrical Current transformers and is very important factor to choose a CT. It is the voltage at which a CT gets saturated.(CT-current transformer).
What is reverse power relay?
Reverse Power flow relay are used in generating stations's protection. A generating stations is supposed to fed power to the grid and in case generating units are off,there is no generation in the plant then plant may take power from grid. To stop the flow of power from grid to generator we use reverse power relay.
Reverse Power flow relay are used in generating stations's protection. A generating stations is supposed to fed power to the grid and in case generating units are off,there is no generation in the plant then plant may take power from grid. To stop the flow of power from grid to generator we use reverse power relay.
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What will happen if DC supply is given on the primary of a transformer?
Mainly transformer has high inductance and low resistance.In case of DC supply there is no inductance ,only resistance will act in the electrical circuit. So high electrical current will flow through primary side of the transformer.So for this reason coil and insulation will burn out.
Mainly transformer has high inductance and low resistance.In case of DC supply there is no inductance ,only resistance will act in the electrical circuit. So high electrical current will flow through primary side of the transformer.So for this reason coil and insulation will burn out.
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What is the difference between isolators and electrical circuit breakers? What is bus-bar?
Isolators are mainly for switching purpose under normal conditions but they cannot operate in fault conditions .Actually they used for isolating the CBs for maintenance. Whereas CB gets activated under fault conditions according to the fault detected.Bus bar is nothing but a junction where the power is getting distributed for independent loads.
Isolators are mainly for switching purpose under normal conditions but they cannot operate in fault conditions .Actually they used for isolating the CBs for maintenance. Whereas CB gets activated under fault conditions according to the fault detected.Bus bar is nothing but a junction where the power is getting distributed for independent loads.
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