O.C & S.C Test, Sumpner or back to back Test, Condition for maximum efficienc...Abhishek Choksi
Sub: DC Machines and Transformer (2130904)
Active Learning Assignment
Topic: O.C & S.C Test, Sumpner or back to back Test, Condition for maximum efficiency, All day Efficiency
O.C & S.C Test, Sumpner or back to back Test, Condition for maximum efficienc...Abhishek Choksi
Sub: DC Machines and Transformer (2130904)
Active Learning Assignment
Topic: O.C & S.C Test, Sumpner or back to back Test, Condition for maximum efficiency, All day Efficiency
To understand the basic working principle of a transformer.
To obtain the equivalent circuit parameters from Open circuit and Short circuit tests, and to estimate efficiency & regulation at various loads.
To understand the basic working principle of a transformer.
To obtain the equivalent circuit parameters from Open circuit and Short circuit tests, and to estimate efficiency & regulation at various loads.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
2. What is a Transformer?
• A transformer is a static electrical machine which transfers electrical
energy from one circuit to another without changing the frequency.
• Which raises or lowers voltage or current at the same frequency.
• It works on the principle of MUTUAL INDUCTION.
3. Transformer
• It consists of two windings insulated from each other and wound on a
common core made up of a magnetic material.
• AC voltage is connected across one of the windings called primary
winding.
• Load is connected to the other winding called the secondary winding.
• In both windings, EMF is induced by electromagnetic induction.
5. Constructional details
Main Components of a Transformer are,
Magnetic core
Primary & Secondary windings
Insulation of windings
Conservator tank & Explosion vent
Bushings
Buchholz relay
Breather
Cooling arrangements
6. Magnetic Core
• Magnetic circuit consists of an iron
core.
• Core is made up of stacks of thin
laminations (0.35mm thickness) of Cold
Rolled Grain Oriented (CRGO) silicon
steel.
• These laminations are lightly insulated
with varnish.
• Two types of magnetic circuit are core
type and shell type.
8. Core type construction
• In the core type, the windings are wound around two legs of a
rectangular magnetic core.
• Windings surround the core & it has only one magnetic path.
9. Shell type construction
• In shell type, the windings are wound around the center leg of a
three-legged core
• Core surrounds the windings.
10. Windings
• A transformer has two windings namely primary and secondary.
• These windings consist of a series of turns called coils, wound around
the core.
• Transformer windings are made of solid or stranded copper or
aluminium strip conductors.
11. Conservator and Explosion Vent
• Conservator is used to provide adequate
space for the expansion of oil when
transformer is loaded or when ambient
temperature changes.
• Explosion Vent is used to discharge excess
pressure developed inside the transformer
during loading, to the atmosphere.
12. Breather
• It sucks the moisture from the air which is taken by transformer so that
dry air is taken by transformer.
13. Bushings
• Transformers are connected to high voltage
lines.
• Extreme care should be taken to prevent the
conductors touching the transformer tank.
• So the connections in and out of the
transformer are made by the use of bushings.
• Bushings are normally porcelain insulators.
14. Buchholz Relay
• It is a safety device connected between main tank and
conservator tank.
• In case of slow developing faults, it sounds an alarm to
alert the operator.
• If serious fault occur in the transformer, it disconnects the
transformer to protect it.
15. Methods of Cooling of Transformers
• Air natural
• Air Blast
• Oil natural
• Oil blast
• Forced circulation of oil
• Oil and water cooled
• Forced oil and water cooled
16. Losses in a Transformer
• The power losses in a transformer are of two types, namely;
Core or Iron losses
Copper losses
17. Core or Iron losses (Pi)
• This loss consists of hysteresis and eddy current loss and occur in
the transformer core due to the alternating flux.
• These losses can be determined by open-circuit test.
Hysteresis loss, Ph = Kh Bmax
1.6 f v watts
Eddy current loss, Pe = Ke Bmax
2 f2 t2v watts
• Both the above losses depend on Bm and frequency which are
constant.
• Hence, core or iron losses are practically the same at all loads.
18. Copper losses (PC)
• These losses occur in both the primary and secondary windings due to
their ohmic resistance.
• These losses can be determined by short-circuit test.
𝑃𝐶 = 𝐼1
2
𝑅1 + 𝐼2
2
𝑅2 = 𝐼1
2
𝑅01 = 𝐼2
2
𝑅02
• Copper losses vary as the square of load current.
• Copper losses account for about 90% of the total losses.
19. Summary
Core loss
It is the Constant loss
Does not change even as the
load current changes
Proportional to supply voltage
and frequency
Copper loss or I2R loss
It is a variable loss
Also called as I2R loss
Proportional to square of the load
current
Occurs in the winding resistances
It is dissipated as heat
21. • When transferring resistance or reactance from primary to secondary,
multiply it by K2.
• When transferring resistance or reactance from secondary to primary,
divide it by K2.
Shifting Impedances
28. Testing of Transformers
• The circuit constants, efficiency and voltage regulation of a
transformer can be determined by two simple tests.
(i) Open-circuit test
(ii) Short-circuit lest
29. Open Circuit Test
This test is conducted to determine R0 & X0
Rated voltage is applied on LV side & HV side is kept open.
At no load, current taken by the transformer is 3-5% of full load
current. So I2R loss is negligible.
Therefore power consumed by the transformer on no load is
considered as core loss.
30. Open Circuit Test
Data observed from the test
Supply voltage = V0 volts
No load current = I0 amps
Iron losses = W0 watts
W0 = V0I0 CosФ0
CosФ0 = W0/(V0I0)
IW = I0 CosФ0
Im = I0 SinФ0
R0 = V1/IW
X0 = V1/Im
31. Short Circuit Test
This test is conducted to determine R02 & X02
LV side of the Tfr is short circuited & the test is conducted on HV side.
A low voltage is applied on the HV side to circulate the rated current
on both the windings.
Power drawn during this test is considered as copper loss.
32. Short Circuit Test
Data observed from the test
Applied voltage = VSC volts
Short circuit current = ISC amps
Copper losses = WSC watts
WSC = ISC
2R02
R02= WSC/ISC
2
Z02=VSC/ISC
X02=[Z02
2-R02
2]1/2
33. Efficiency
• F.L. Iron loss = Pi ...from open-circuit test
• F.L. Cu loss = PC ...from short-circuit test
• Total losses = Pi + PC
• Full-load efficiency of the transformer at any p.f.
F. L. efficiency, ηfl =
Full load VA × P. F
Full load VA × P. F + Pi + PC
34. Efficiency
• At any load (X times full-load), the total losses will be
𝑃𝑇 = 𝑃𝑖 + 𝑋2
𝑃𝐶
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑎𝑡 𝑋 𝑙𝑜𝑎𝑑, 𝜂𝑋 =
(𝑋 × 𝐹𝑢𝑙𝑙 𝑙𝑜𝑎𝑑 𝑉𝐴 × 𝑃. 𝐹)
𝑋 × 𝐹𝑢𝑙𝑙 𝑙𝑜𝑎𝑑 𝑉𝐴 × 𝑃. 𝐹 + 𝑃𝑖 + 𝑋2𝑃𝐶
• Note that iron loss remains the same at all loads.
35. Condition for Maximum Efficiency
𝑂𝑢𝑡𝑝𝑢𝑡 𝑃𝑜𝑤𝑒𝑟 = 𝑉2𝐼2 𝑐𝑜𝑠 𝛷2
If R02 is the total resistance of the transformer referred to secondary, then,
𝑇𝑜𝑡𝑎𝑙 𝐶𝑜𝑝𝑝𝑒𝑟 𝑙𝑜𝑠𝑠, 𝑃𝐶 = 𝐼2
2
. 𝑅02
𝑇𝑜𝑡𝑎𝑙 𝑙𝑜𝑠𝑠𝑒𝑠 = 𝑃𝑖 + 𝑃𝐶
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦, 𝜂 =
𝑉2𝐼2 𝑐𝑜𝑠 𝛷2
𝑉2𝐼2 𝑐𝑜𝑠 𝛷2 + 𝑃𝑖 + 𝐼2
2
. 𝑅02
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦, 𝜂 =
𝑉2 𝑐𝑜𝑠 𝛷2
𝑉2 𝑐𝑜𝑠 𝛷2 +
𝑃𝑖
𝐼2
+ 𝐼2 . 𝑅02
36. Condition for Maximum Efficiency
𝑑
𝑑𝐼2
𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 = 0
𝑑
𝑑𝐼2
V2 cos Φ2 +
Pi
I2
+ I2 . R02 = 0
0 −
𝑃𝑖
𝐼2
2 + R02 = 0
𝑃𝑖 = 𝐼2
2
R02
• i.e, Iron loss = Copper loss
37. Condition for Maximum Efficiency
• Hence efficiency of a transformer will be maximum when copper
losses are equal to iron losses.
• From above equation, the load current I2 corresponding to maximum
efficiency is given by,
𝐼2 =
𝑃𝑖
R02
38. Output kVA Corresponding to Maximum Efficiency
• PC = Copper losses at full-load kVA
• Pi = Iron losses
• X = Fraction of full-load kVA at which efficiency is maximum
• Total Cu losses = X2 PC
• For maximum efficiency, Pi = X2 PC
∴ X =
Pi
PC
39. Output kVA Corresponding to Maximum Efficiency
Output kVA corresponding to max. efficiency = 𝑋 × Full load kVA
Output kVA corresponding to max. efficiency = Full load kVA ×
Pi
PC
• It may be noted that the value of kVA, at which the efficiency is
maximum, is independent of p.f. of the load.
40. Voltage Regulation
• Change in secondary terminal voltage, when full load at a given power
factor and at rated voltage is thrown off, is expressed as a percentage
of rated terminal voltage.
• The change in secondary terminal voltage from no load to full load
expressed as a percentage of full load voltage.
% 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝑹𝒆𝒈𝒖𝒍𝒂𝒕𝒊𝒐𝒏 =
𝑽𝟐 𝑵.𝑳 − 𝑽𝟐 𝑭.𝑳
𝑽𝟐 𝑭.𝑳
× 𝟏𝟎𝟎%
41. Voltage Regulation at Different Power factors
• Voltage regulation for lagging p.f at load X,
% 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 𝒓𝒆𝒈𝒖𝒍𝒂𝒕𝒊𝒐𝒏 =
𝑿. 𝑰𝟐 𝑹𝟎𝟐 𝐜𝐨𝐬 𝝓𝟐 + 𝑿𝟎𝟐 𝐬𝐢𝐧 𝝓𝟐
𝑽𝟐
× 𝟏𝟎𝟎%
• Voltage regulation at leading p.f at load X,
% 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 𝒓𝒆𝒈𝒖𝒍𝒂𝒕𝒊𝒐𝒏 =
𝑿. 𝑰𝟐 𝑹𝟎𝟐 𝐜𝐨𝐬 𝝓𝟐 − 𝑿𝟎𝟐 𝐬𝐢𝐧 𝝓𝟐
𝑽𝟐
× 𝟏𝟎𝟎%
• Voltage regulation at Unity p.f at load X,
% 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 𝒓𝒆𝒈𝒖𝒍𝒂𝒕𝒊𝒐𝒏 =
𝑿. 𝑰𝟐. 𝑹𝟎𝟐
𝑽𝟐
× 𝟏𝟎𝟎%
42. In a 25 kVA, 2000 V / 200 V transformer, the constant and
variable losses are 350 W and 400 W respectively. Calculate the
efficiency on unity power factor at full load and half the full
load.
43. Calculate the efficiency at half and full load of a 100 kVA
transformer for unity and 0.8 p.f. The copper loss is 1000 W at
full load and iron loss is 1000 W.
44. Obtain the equivalent circuit of a 200 / 400 V, 50 Hz, 1 phase
transformer from the following test data:
O.C. test: 200 V, 0.7 A, 70 W – on L.V side.
S.C. test: 15 V, 10 A, 85 W – on H.V side.
Calculate the secondary voltage when delivering 5 kW at 0.8 p.f
lagging, the primary voltage being 200 V.
45. From OC Test
P0 = V0I0 cos ϕ0
cos ϕ0 =
P0
V0I0
=
70
200 × 0.7
cos ϕ0 = 0.5
sin ϕ0 = 0.866
Iw = I0 cos ϕ0 = 0.7 × 0.5 = 0.35𝐴
Im = I0 sin ϕ0 = 0.7 × 0.866 = 0.606𝐴
R0 =
V0
Iw
=
70
0.35
= 200 Ω
X0 =
V0
Im
=
70
0.606
= 115.5 Ω
From SC Test
Psc = Isc
2 R02
R02 =
Psc
Isc
2 =
85
102
= 0.85 Ω
Z02 =
Vsc
Isc
=
15
10
= 1.5 Ω
X02 = Z02
2
− R02
2
X02 = 1.52 − 0.852
X02 = 1.235 Ω
46. Equivalent Circuit Referred to Primary Side
𝐾 =
400
200
= 2
R01 =
0.85
22
= 0.212 Ω
X01 =
1.235
22
= 0.308 Ω
48. • Load kVA corresponding to 5 kW is,
=
5000
0.8
= 6250 𝑉𝐴
• Load current I2 while delivering 6250 VA is,
=
6250
400
= 15.625 𝐴
• Total voltage drop in secondary when it carries 15.625 A is,
= 𝐼2 𝑅02 𝑐𝑜𝑠 𝜙2 + 𝑋02 𝑠𝑖𝑛 𝜙2
= 15.625 0.85 × 0.8 + 1.235 × 0.6
= 22.20 𝑉
• Hence the secondary voltage is,
𝑉2 = 400 − 22.2 = 377.8 𝑉
49. All Day Efficiency
• The ordinary or commercial efficiency of a transformer is defined as
the ratio of output power to the input power i.e.,
Commercial efficiency =
Output power
Input power
Primaries of distribution transformers are energized all the 24 hours in a
day but the secondary windings supply little or no load during the major
portion of the day.
50. All Day Efficiency
• Constant loss occurs during the whole day but copper loss occurs only
when the transformer is loaded.
• The performance of such transformers is judged on the basis of energy
consumption during the whole day (i.e., 24 hours).
• This is known as all-day or energy efficiency.
51. All Day Efficiency
• The ratio of output in kWh to the input in kWh of a transformer over
a 24-hour period is known as all-day efficiency i.e.,
𝜂𝑎𝑙𝑙−𝑑𝑎𝑦 =
𝑘𝑊ℎ 𝑜𝑢𝑡𝑝𝑢𝑡 𝑖𝑛 24 ℎ𝑜𝑢𝑟𝑠
𝑘𝑊ℎ 𝑖𝑛𝑝𝑢𝑡 𝑖𝑛 24 ℎ𝑜𝑢𝑟𝑠
• In the design of such transformers, efforts should be made to reduce
the iron losses which continuously occur during the whole day.
52. All Day Efficiency
• A 40kVA distribution transformer has iron loss of 500 W and full load
copper loss of 500 W. the transformer is supplying a lighting load. The
load cycle is as under: Full load for 4 hours, half load for 8 hours and
no load for 12 hours. Calculate the all day efficiency.
53. All Day Efficiency
• A transformer has its maximum efficiency of 0.98 at 15 kVA at UPF.
During the day it is loaded as follows:
Duration Load Power Factor
12 hours 2 kW at 0.5 p.f
6 hours 12 kW at 0.8 p.f
4 hours 18 kW at 0.9 p.f
2 hours No load
• Find the “All Day Efficiency”.
55. Polarity Test
• Similar polarity ends of two windings are those ends that acquire
positive and negative polarity of emf induced in them simultaneously.
56. Auto Transformer
• An autotransformer has a single winding on an iron core and a part of
winding is common to both the primary and secondary circuits.
57. Auto Transformer
• Primary and secondary windings are connected electrically as well as
magnetically.
• Therefore, power from the primary is transferred to the secondary
conductively as well as inductively (transformer action).
• The voltage transformation ratio K of an ideal autotransformer is,
𝐸1
𝐸2
=
𝑁1
𝑁2
=
𝑉1
𝑉2
=
𝐼2
𝐼1
= 𝐾
58. Advantages of Autotransformers
• An autotransformer requires less Cu than a two -winding transformer of
similar rating.
• Autotransformer operates at a higher efficiency than a two-winding
transformer of similar rating.
• An autotransformer has better voltage regulation than a two-winding
transformer of the same rating.
• An autotransformer has smaller size than a two-winding transformer of the
same rating.
59. Advantages of Autotransformers
• An autotransformer requires smaller exciting current than a two-
winding transformer of the same rating.
• These advantages decrease as the ratio of transformation increases. So
an autotransformer has advantages only for low values of
transformation ratio.
60. Disadvantages of Autotransformers
• There is a direct connection between the primary and secondary.
Therefore, the output is no longer isolated from the input.
• It is not safe for stepping down a high voltage to a low voltage.
• The short - circuit current is much larger than for the two-winding
transformer of the same rating.
• This reduces the effective resistance and reactance.
61. Applications of Autotransformers
• Autotransformers are used to compensate for voltage drops in
transmission and distribution lines. When used for this purpose, they
are known as booster transformers.
• Autotransformers are used for reducing the voltage supplied to a.c.
motors during the starting period.
• Autotransformers are used for continuous variable supply.
62. Three Phase Transformers
• Large scale generation of electric power is usually 3 phase at 13.2 kV
or higher.
• But transmission voltage is 110 kV, 132 kV and 400 kV.
• Generated voltage needs to be increased.
• Hence 3 phase transformers are used.
• 3 single phase transformers can be used to construct a 3 phase
transformer.
• But it occupies more space and 15% more costlier than using a single
unit.