This document discusses different methods for turning on or triggering an SCR (silicon controlled rectifier). It describes gate triggering as the most common and efficient method, where a positive voltage applied between the gate and cathode terminals injects electrons to cause breakdown at junction J2. It also discusses forward voltage, temperature, dv/dt, and light triggering but indicates they have disadvantages like requiring high voltages, causing thermal runaway, or producing high voltage spikes. Pulse triggering with a single pulse or train of pulses through a pulse transformer is highlighted as the most popular gate triggering method to reduce gate losses.
This ppt provides a brief overview on thyristors commonly known as SCRs. V- I characteristics curve, triggering methods, protection methods, series and parallel operations of SCRs, applications are discussed in this slide.
As we have discussed that out of various triggering methods to turn the SCR, gate triggering is the most efficient and reliable method. Most of the control applications use this type of triggering because the desired instant of SCR turning is possible with gate triggering method.
This ppt provides a brief overview on thyristors commonly known as SCRs. V- I characteristics curve, triggering methods, protection methods, series and parallel operations of SCRs, applications are discussed in this slide.
As we have discussed that out of various triggering methods to turn the SCR, gate triggering is the most efficient and reliable method. Most of the control applications use this type of triggering because the desired instant of SCR turning is possible with gate triggering method.
A silicon-controlled rectifier or semiconductor-controlled rectifier is a four-layer solid-state current-controlling device. Some sources define silicon-controlled rectifiers and thyristors as synonymous,[5] other sources define silicon-controlled rectifiers as a proper subset of the set of thyristors. SCRs are mainly used in devices where the control of high power, possibly coupled with high voltage, is demanded. Their operation makes them suitable for use in medium- to high-voltage AC power control applications, such as lamp dimming, power regulators and motor control.
Original Uni-junction transistor or UJT is a simple device in which a bar of N-type semiconductor material into which P-type material is diffused; somewhere along its length defining the device parameter as intrinsic standoff. The 2N2646 is the most commonly used version of UJT.
A silicon controlled rectifier or semiconductor controlled rectifier is a four-layer solid-state current-controlling device. The principle of four-layer p–n–p–n switching was developed by Moll, Tanenbaum, Goldey and Holonyak of Bell Laboratories in 1956.
For more notes on basics of electronics will see on https://www.slideshare.net/ATHEENAMILAGIPANDIAN/edit_my_uploads
To turn on a Thyristor, there are various triggering methods in which a trigger pulse is applied at its Gate terminal. Similarly, there are various techniques to turn off a Thyristor, these techniques are called Thyristor Commutation Techniques.
Speed control in 3 phase induction motorKakul Gupta
Speed control in induction motors is required for efficient operation
Various methods of speed control through semiconductor devices:
1. Stator voltage control
2. Stator frequency control
3. Stator voltage control
4. Stator current control
5. Static Rotor Resistance Control
6. Slip Energy Recovery Control
The complete list of thyristor family members include diac (bidirectional diode thyristor), triac (bidirectional triode thyristor), SCR (silicon controlled rectifier), Shockley diode, SCS (silicon controlled switch), SBS (silicon bilateral switch), SUS (silicon unilateral switch) also known as complementary SCR or CSCR, LASCR (light activated SCR), LAS (light activated switch) and LASCS (light activated SCS).
A silicon-controlled rectifier or semiconductor-controlled rectifier is a four-layer solid-state current-controlling device. Some sources define silicon-controlled rectifiers and thyristors as synonymous,[5] other sources define silicon-controlled rectifiers as a proper subset of the set of thyristors. SCRs are mainly used in devices where the control of high power, possibly coupled with high voltage, is demanded. Their operation makes them suitable for use in medium- to high-voltage AC power control applications, such as lamp dimming, power regulators and motor control.
Original Uni-junction transistor or UJT is a simple device in which a bar of N-type semiconductor material into which P-type material is diffused; somewhere along its length defining the device parameter as intrinsic standoff. The 2N2646 is the most commonly used version of UJT.
A silicon controlled rectifier or semiconductor controlled rectifier is a four-layer solid-state current-controlling device. The principle of four-layer p–n–p–n switching was developed by Moll, Tanenbaum, Goldey and Holonyak of Bell Laboratories in 1956.
For more notes on basics of electronics will see on https://www.slideshare.net/ATHEENAMILAGIPANDIAN/edit_my_uploads
To turn on a Thyristor, there are various triggering methods in which a trigger pulse is applied at its Gate terminal. Similarly, there are various techniques to turn off a Thyristor, these techniques are called Thyristor Commutation Techniques.
Speed control in 3 phase induction motorKakul Gupta
Speed control in induction motors is required for efficient operation
Various methods of speed control through semiconductor devices:
1. Stator voltage control
2. Stator frequency control
3. Stator voltage control
4. Stator current control
5. Static Rotor Resistance Control
6. Slip Energy Recovery Control
The complete list of thyristor family members include diac (bidirectional diode thyristor), triac (bidirectional triode thyristor), SCR (silicon controlled rectifier), Shockley diode, SCS (silicon controlled switch), SBS (silicon bilateral switch), SUS (silicon unilateral switch) also known as complementary SCR or CSCR, LASCR (light activated SCR), LAS (light activated switch) and LASCS (light activated SCS).
SCRs are mainly used in devices where the control of high power, possibly coupled with high voltage, is demanded. Their operation makes them suitable for use in medium- to high-voltage AC power control applications, such as lamp dimming, power regulators and motor control.
Silicon Controlled Rectifier (SCR) is a unidirectional semiconductor device made of silicon.SCR is a three-terminal, four-layer semiconductor device consisting of alternate layers of p-type and n-type material.
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My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
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Vaccine management system project report documentation..pdfKamal Acharya
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Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
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4. Gate characteristic of thyristor or SCR
• Gate characteristic of thyristor or SCR gives us a brief idea
to operate it within a safe region of applied
gate voltage and current.
• So this is a very important characteristic regarding thyristor.
• At the time of manufacturing each SCR or thyristor is
specified with the maximum gate voltage limit (Vg-max), gate
current limit (Ig-max) and maximum average gate power
dissipation limit (Pgav).
• These limits should not be exceeded to protect the SCR
from damage and there is also a specified minimum voltage
(Vg-min) and minimum current (Ig-min) for proper operation of
thyristor.
5. • Curve 1 represents the lowest voltage values
that must be applied to turn on the SCR and
curve 2 represents the highest values of the
voltage that can safely applied. So from the
figure we can see the safety operated area of
SCR is bcdefghb.
6. Introduction
• SCR has two stable states IN FIRST QUADRANT
Forward blocking and
Forward conduction state.
• Switching the SCR from forward blocking state
(OFF- state) to forward conduction state (ON-
state) is known as turning ON process of SCR.
• It is also called as triggering.
7. Intro…
• With a voltage applied to the SCR, if the anode
is made positive with respect to the cathode,
the SCR becomes forward biased.
• The SCR can be made to conduct or switching
into conduction mode BY FOLLOWING
METHODS……
8. Turn on methods
• Forward voltage triggering
• Temperature triggering
• dv/dt triggering
• Light triggering
• Gate triggering
9. Forward Voltage Triggering
• By increasing the forward anode to cathode
voltage, the depletion layer width is also
increased at junction J2.
• It causes increase in minority charge carriers.
• This further leads to an avalanche breakdown
of the junction J2 at a forward breakover
voltage VBO.
10. Forward Voltage Triggering
• In practice this method is not employed
because it needs a very large anode to
cathode voltage.
• Once the voltage is more than the VBO, it
generates very high currents which may cause
damage to the SCR.
• Therefore, in most of the cases this type of
triggering is avoided.
11. Temperature Triggering
• The reverse leakage current depends on the
temperature.
• If the temperature is increased to a certain value, the
number of hole-pairs also increases.
• This causes to increase the leakage current and further
it increases the current gains of the SCR.
• This starts the regenerative action inside the SCR since
the (α1 + α2) value approaches to unity (as the current
gains increases).
• By increasing the temperature at junction J2 causes the
breakdown of the junction and hence it conducts.
12. Temperature Triggering
• By increasing the temperature at junction J2
causes the breakdown of the junction and
hence it conducts.
• This type of triggering is practically not
employed because it causes the thermal
runaway and hence the device or SCR may be
damaged.
13. dv/dt Triggering
• In forward blocking state junctions J1 and J3 are
forward biased and J2 is reverse biased.
• So the junction J2 behaves as a capacitor (of two
conducting plates J1 and J3 with a dielectric J2)
due to the space charges in the depletion region.
The charging current of the capacitor is given as
I = C dv/ dt
dv/dt is the rate of change of applied voltage and C
is the junction capacitance.
14. dv/dt Triggering
• From the above equation, if the rate of change of
the applied voltage is large that leads to increase
the charging current which is enough to increase
the value of alpha.
• So the SCR becomes turned ON without a gate
signal.
• However, this method is also practically avoided
because it is a false turn ON process and also this
can produce very high voltage spikes across the
SCR so there will be considerable damage to it.
15. Light Triggering
• An SCR turned ON by light radiation is also
called as Light Activated SCR (LASCR).
• This type of triggering is employed for phase
controlled converters in HVDC transmission
systems.
• In this method, light rays with appropriate
wavelength and intensity are allowed to strike
the junction J2.
16. Light Triggering
• These types of SCRs are consisting a niche in
the inner p-layer.
• Therefore, when the light struck on this niche,
electron-hole pairs are generated at the
junction J2 which provides additional charge
carriers at the junction leads to turn ON the
SCR.
17. Gate Triggering
• This is most common and efficient method to
turn ON the SCR.
• When the SCR is forward biased, a sufficient
voltage at the gate terminal injects some
electrons into the junction J2.
• This result to increase reverse leakage current
and hence the breakdown of junction J2 even
at the voltage lower than the VBO.
18. Gate Triggering
• In gate triggering method, a positive voltage
applied between the gate and the cathode
terminals.
• We can use three types of gate signals to turn
On the SCR.
DC signal,
AC signal and
pulse signal
19. DC Gate Triggering
• In this triggering, a sufficient DC voltage is
applied between the gate and cathode
terminals in such a way that the gate is made
positive with respect to the cathode.
• The gate current drives the SCR into
conduction mode.
• In this, a continuous gate signal is applied at
the gate and hence causes the internal power
dissipation (or more power loss).
20. AC Triggering
• This is the most commonly used method for
AC applications where the SCR is employed for
such applications as a switching device.
• With the proper isolation between the power
and control circuit, the SCR is triggered by the
phase-shift AC voltage derived from the main
supply.
• The firing angle is controlled by changing the
phase angle of the gate signal.
21. Pulse Triggering
• The most popular method of triggering the SCR is
the pulse triggering.
• In this method, gate is supplied with single pulse
or a train of pulses.
• The main advantage of this method is that gate
drive is discontinuous or doesn’t need continuous
pulses to turn the SCR and hence gate losses are
reduced in greater amount by applying single or
periodically appearing pulses.
• For isolating the gate drive from the main supply,
a pulse transformer is used.