The document discusses different methods of turning on a thyristor, including temperature triggering, light triggering, forward voltage triggering, and dv/dt triggering. It then describes the most common method - gate triggering using a firing circuit. Various firing circuit designs are discussed, including resistance, RC, UJT, and pulse transformer circuits. The pulse transformer circuit provides electrical isolation between the low voltage gate circuit and the high voltage power circuit. Proper design of the firing circuit is important to reliably turn on the thyristor at the desired time.
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.
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.
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.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
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.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
CW RADAR, FMCW RADAR, FMCW ALTIMETER, AND THEIR PARAMETERSveerababupersonal22
It consists of cw radar and fmcw radar ,range measurement,if amplifier and fmcw altimeterThe CW radar operates using continuous wave transmission, while the FMCW radar employs frequency-modulated continuous wave technology. Range measurement is a crucial aspect of radar systems, providing information about the distance to a target. The IF amplifier plays a key role in signal processing, amplifying intermediate frequency signals for further analysis. The FMCW altimeter utilizes frequency-modulated continuous wave technology to accurately measure altitude above a reference point.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...
Pex ppt.pdf
1. THYISTOR TURN-ON.
A thyristor is turned on by increasing the anode
current. This can be accomplished in one of the
following ways.
1. Temperature Triggering.
If the temperature of a thyristor is high, there will be an
increase in the number of electron hole pairs, which
would increase the leakage current. This increase in
currents would cause‘1’ and ‘2’ to increase. Due to
regenrative action,(1 +2 ) may tend to be unity and
the thyristor may be turned on. This type of turn-on
may cause thermal runaway and is normally avoided.
2. Light Triggering.
When light is thrown on the gate-cathode junction
through a light window, the electron-hole pairs will
increase ( free charge carriers electrons and holes are
generated ). If the intensity of this light exceeds a
certain value, the thyristor is turned on.Such a thyristor
is known as light activated SCR (LASCR).
2. 3. Forward Voltage Triggering.
When the forward anode to cathode is greater than the
forward breakdown voltage VBO.
Sufficient leakage current will flow to initiate
regenrative turn-on. This type of turn-on may be
destructive and should be avoided.
4. dv / dt Triggering.
With forward voltage across the anode and cathode of
a thyristor, the two junctions are forward biased but the
inner junction J2 is reverse biased.This junction has
the characteristics of a capacitive due to charges
existing across the junction.If the entire anode to
cathode forward voltage Va appears across junction J2
and the charge is denoted by ‘q’ than a charging
current ‘I’ given by equation
Gate Triggering. The gate triggering is the most common
method of turning on the SCRs, because this method lends itself
accurately for turning on the SCRs at the desired instant of time
3. I = (dq / d t), d (Cj , Va )/ d t Cj dVa / d t + Va
dCj / d t
As Cj, the capacitive of junction ‘J2’ is almost constant,
the current is given by
i = Cj dVa / d t
If the rate of rise of forward voltage ‘dVa / d t’ is high,
the charging current plays the role of gate current and
turns on the thyristor even when gate signal is zero.
Such phenomena of turning on a thyristor, called ‘dVa
/ d t’ turn-on, must be avoided as it leads to false
operation of the thyristor circuit. For controllable
operation of the thyristor, the rate of rise of forward
anode to cathode voltage ‘dVa / d t’ must be kept
below the specified rated limit. Typically ‘dV / d t’ are
20-500v / sec. False turn-on of a thyristor can be
prevented by using a snubber circuit in parallel with the
device.
4. GATE CURRENT.
If a thyristor is forward biased, the injection of gate
current by applying positive gate voltage between the
gate and cathode terminals would turn on the thyristor.
As the gate current is increased, the forward blocking
voltage is decreased.
The following points should be considered in designing
the gate control circuit:
1. The gate signal should be removed after the
thyristor turned on. A continuous gating signal would
increase the power loss in the gate junction.
2. While thyristor is reverse biased. There should be no
gate signal; otherwise, the thyristor may fail due to an
increased leakage current.
3. The width of gate pulse tG must be longer than the
time required for the anode current to rise to the
holding current value IH. In practice, the pulse width tG
is normally made more than the turn on time ton of the
thyristor
5.
6. FIRING CIRCUITS FOR THYRISTORS
An SCR can be switched from off-state to on-state in
several ways; these are forward voltage triggering,
dv / dt triggering, temperature triggering, light
triggering and gate triggering. The gate triggering is
the most common common method of turning on the
SCRs, because this method lends itself accurately for
turning on the SCRs at the desired instant of time.
MAIN FEATURES OF FIRING CIRCUITS
The most common method for controlling the onset
of conduction in an SCR is by means of gate voltage
control. The gate control circuit is also called firing, or
triggering circuit. These gating circuits are usually low
power electronics circuits. A firing circuit should fulfil
the following two functions.
7. If power circuit has more than one SCR, the firing
circuit should produce gating pulses for each SCR at
the desired instant for proper operation of the power
circuit. These pulses must be periodic in nature and
the sequence of firing must correspond with the type of
thyristorised power controller. For example, in a single
phase converter using two SCRs, the triggering circuit
must produce one firing pulse in each half cycle ; in a
3-phase full converter using six SCRs, gating circuit
must produce one trigger pulse after every 60 degree
interval
The control signal generated by a firing circuit may not
be able to turn –on an SCR. It is therefore common to
feed the voltage pulses to a driver circuit and then to
gate-cathode circuit. A driver circuit consists of a pulse
amplifier and a pulse transformer
8. A firing circuit scheme, in general consists of the components shown
in above fig. . A regulated DC power supply is obtained from an
alternating voltage source. Pulse generator, supplied from both
AC and DC sources, gives out voltage pulses which are then fed
to pulse amplifier for their amplification. Shielded cables transmit
the amplified pulses to pulse transformers. The function of pulse
transformer is to isolate the low voltage gate-cathode circuit from
the high voltage anode-cathode circuit
9. Types of Thyristor Firing Circuits
1. Resistance Firing Circuit
2. RC Firing Circuit
3.UJT Firing Circuit
4.Pulse Transformer Firing Circuit
Resistance Firing Circuit
Resistance triggering circuit is the simplest and the
most economical method.This however, suffer from a
limited range of firing angle control (0 to 90 degree),
great dependence on temperature and differnce in
performance between individual SCRs
R C FIRING CIRCUITS
The limited range of firing angle control by resistance
firing circuit can be overcome by RC firing circuit.
The firing angle control range from 0 degree to 180
degree
10. Types of Thyristor Firing Circuits
UJT triggering circuits.
Resistance and RC triggering circuits give prolonged
pulses. As a result, power dissipation in the gate circuit
is large. This difficulty can be overcome by UJT
triggering circuits.
11. RESISTANCE FIRING CIRCUITS
Theory of operation
As shown in the circuit, R2 is the variable resistance, R
is the stabilizing resistance. In case R2 is zero, gate
current may flow from source, through load, R1, Diode
D, and gate to cathode. This current should not
exceed permissible gate current . This current can be
limit with the value of R1
12. OPERATION OF RESISTANCE FIRING CIRCUITS
It is thus seen that function of R1 is to limit the gate
current to a safe value as R2 is varied.
Resistance R should have such a value that maximum
voltage drop across it does not exceed maximum
possible gate voltage
13. R C FIRING CIRCUITS
The limited range of firing angle control by
resistance firing circuit can be overcome by
RC firing circuit.
14. Theory of operation of RC Firing
Circuit
Fig illustrates RC triggering circuit.
By varying the value of R, firing angle can be
controlled from 0 to 180 degree.
In the negative half cycle, C charges through D2 .
This capacitor voltage remains constant at –Vm until
supply voltage attains zero value.
When capacitor charges to positive voltage equal to
gate trigger voltage Vgt, SCR is fired and after this,
capacitor holds to a small positive voltage.
Diode D1 is used to prevent the breakdown of
cathode to gate junction through D2 during the
negative half cycle.
15. Unijunction Transistor (UJT).
It is a three terminal device . The device input, is
called the emitter, has a resistance which rapidly
decreases when the input voltage reaches a certain
level. This is termed a “negative resistance
characteristics’’.
three terminals called the Emitter (E), Base-one(B1)
and Base-two(B2). It is made up of an N-type base to
which P-type emitter is embedded. P-type emitter is
heavily doped and N-type base is lightly doped
17. UJT Firing Circuit
The unijunction transistor is a highly efficient switch ;
its switching time is in the range of nanoseconds.
Since UJT exhibits negative resistance
characteristics,
Fig. (a) shows a circuit diagram with UJT working in
the oscillator mode. The external resistances R1 R2
are small in comparison with the internal resistances
RB1, RB2 of UJT bases
18. Operation of UJT Firing Circuit
In Fig. (a), when source voltage VBB is applied, capacitor C
begins to charge through R exponentially towards VBB, During
this charging, emitter circuit of UJT is an open circuit. The
capacitor voltage vC, equal to emitter voltage vE, is given by
VC = VE = VBB( 1 – e-t/RC)
The time constant of the charge circuit is 1 = RC
When this emitter voltage vE (or vC) reaches the
peak-point voltage VP (= VBB + VD), the unijunction
between E – B1 breaks down. As a result, UJT turns
on and capacitor C rapidly discharges through low
resistance R1 with a time constant t2 = R1C. Here t2 is
much smaller than t1. When the emitter voltage
decays to the valley-point voltage VV, UJT turns off
19. Pulse Transformer Firing Circuit
Sometimes pulse transformers are used in firing
circuits for thyristors and GTOs, for isolation between
the gate circuit and the load circuit. The main reason
for this is that the load may use a high voltage ac
supply, and the firing circuit may use a low voltage.
The transformer generally used arc either l:l two-
winding, or l'l:l three-winding types. These have
transformers have
a low winding resistance, and a low leakage
resistance. The pulse transformer provides electrical
isolation as it transfers a pulse from the primary 1o the
secondary coil. The secondary coil of the pulse
transformer is connected directly between the gate
and the cathode, or may have series resistor, or a
series diode to prevent reverse gate current.
.
20. There are various ways of connecting the pulse
transformer to trigger the thyristor. Figure shows the
basic pulse transformer coupling to drive a single
thyristor
21. A pulse at the output of the pulse generator is given
to the primary of the pulse transformer, this is
transmitted faithfully at its secondary terminal through
the resistor R to the gate of the thyristor. Figure 3.19
shows another way of using a pulse transformer to
drive an anti-parallel pair of thyristors.
22. Here a three-winding transformer provides complete
isolation and the pulse generator must supply enough
energy to trigger both thyristors. Note the black dots
on the primary and secondary windings. These dots
are used to indicate the polarity of the windings.
Transformer polarity is defined as the relative
direction of the induced voltages in the primary and
secondary windings with respect to the winding
terminals. The dot is used to indicate which windings
have the same instantaneous polarity
23. Pulse Transformers
Pulse transformers are used quite often in firing circuits
for ,SCRs and GTOs. This transformer has usually two
secondaries. The turns ratio from primary to the two
secondaries is 2:1:1 or 1:1:1. These transformers are
designed to have low winding resistance, low leakage
reactar~ce and Iow interwinding capacitance. The
advantages of using pulse transformers in triggering
semiconductor devices are:
(a) They provide isolation of low voltage firing circuit
from high voltage anode-cathode power circuit and
(a) The trigger pulse can be coupled to one or more
devices from the same trigger source by means of pulse
transformer.
A square pulse at the primary terminals of a pulse
transformer may be transmitted at its secondary
terminals faithfully as a square wave or it may be
24. transmitted as a derivative of the input waveform.
A general layout of the trigger circuit using a pulse
transformer is shown in Fig. 2 Here, R1 limits the current
in the primary circuit of pulse transformer. In practice,
trigger pulses are preferred due to the following reasons:
25. (a) This pulse waveform is suitable for injecting a large
charge in the gate circuit for reliable turn on.
(b) The duration of this pulse is small, and therefore, no
significant heating of the gate circuit is observed.
(c) The fact stated (b) as mentioned permits Va to be
raised to a suitable high value so that a hard drive of
SCR is obtained. A device with a hard drive can
withstand high di/dt at the anode circuit, which is
desirable.