Download A transformer is a device that transfers electrical energy from

Unit 6 Transformers
Lead-in
What applications of transformers do you know?
Basic principles
Task 1
Match the words and phrases with the translations.
1. magnetic field
a) strumień magnetyczny
2. induced voltage
b) rdzeń ferromagnetyczny
3. conductors
c) obwód
4. primary voltage
d) napięcie pierwotne (zasilające)
5. circuit
e) cewki
6. number of turns
f) (tutaj) zwiększany
7. winding
g) pole magnetyczne
8. stepped up
h) napięcie indukowane
9. power transmission
i) przewodniki
10. ferromagnetic core
j) sieci elektryczne
11. electronic circuits
k) ilość zwojów
12. stepped down
l) przesyłanie energii
13. coils
m) obwód elektroniczny
14. mutual induction
n) (tutaj) zmniejszany
15. power grids
o) indukcja wzajemna
16. magnetic flux
p) siła elektromotoryczna
17. electromotive force
q) uzwojenie
Task 2
Read the text about transformers and complete it with the words and phrases from Task 1.
magnetic field
winding
mutual induction
conductors
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled (1)…………………… – the transformer’s coils. A varying current in the
first or primary (2)………………….creates a varying magnetic flux in the transformer’s core,
and thus a varying (3)………………………….. through the secondary winding. This varying
magnetic field induces a varying electromotive force (EMF) or “voltage” in the secondary
winding. This effect is called (4)………………………………..
number of turns
primary voltage
ferromagnetic core induced voltage
If a load is connected to the secondary, an electric current will flow in the secondary winding
and electrical energy will be transferred from the primary circuit through the transformer to
the load. In an ideal transformer, the (5)………………………….. in the secondary winding
By Justyna Plezia and Magdalena Potręć (AGH UST)
1
For classroom use at AGH UST . You can distribute the copies in paper and electronic form among fellow teachers and second cycle
students at AGH UST only. Some sections may contain copyrighted material and can be used for educational purposes only and cannot
be made publicly available.
(VS) is in proportion to the (6)……………………………. (VP), and is given by the ratio of the
(7)……………………………… in the secondary (NS) to the number of turns in the primary
(NP) as follows:
By appropriate selection of the ratio of turns, a transformer thus allows an alternating current
(AC) voltage to be “stepped up” by making N S greater than NP, or “stepped down” by making
NS less than NP.
In the vast majority of transformers, the windings are coils wound around a (8)
………………………………, air-core transformers being a notable exception.
power transmission
power grids
electronic circuits
Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage
microphone to huge units weighing hundreds of tons used to interconnect portions of (9)
…………………………….. All operate with the same basic principles, although the range of
designs is wide. While new technologies have eliminated the need for transformers in some
(10)……………………………., transformers are still found in nearly all electronic devices
designed for household (“mains”) voltage. Transformers are essential for high voltage (11)
……………………………….., which makes long distance transmission economically
practical.
Adapted from http://en.wikipedia.org
Task 3
Label the diagram of an ideal transformer.
Primary voltage
Secondary current
Transformer core
Secondary voltage
Primary winding
Primary current
Secondary winding
Adapted from http://en.wikipedia.org/wiki/Transformer
By Justyna Plezia and Magdalena Potręć (AGH UST)
For classroom use at AGH UST . You can distribute the copies in paper and electronic form among fellow teachers and second cycle
students at AGH UST only. Some sections may contain copyrighted material and can be used for educational purposes only and cannot
be made publicly available.
2
Types and construction of transformers
Task 4
a) Match the names with the descriptions.
Power transformers
Auto transformer
Instrument potential transformer
Distribution transformers Instrument current transformer
Control transformers
Isolation transformers
Transformers are constructed so that their characteristics match the application for which they
are intended. The differences in construction may involve the size of the windings or the
relationship between the primary and secondary windings. Transformer types are also
designated by the function the transformer serves in a circuit.
A .............................................................. are generally used in electrical power distribution
and transmission systems. This class of transformers has the highest power, or volt-ampere
ratings, and the highest continuous voltage rating. The power rating is normally determined
by the type of cooling methods the transformer may use. Some commonly-used methods of
cooling are by using oil or some other heat-conducting material. Ampere rating is increased in
a distribution transformer by increasing the size of the primary and secondary windings;
voltage ratings are increased by increasing the voltage rating of the insulation used in making
the transformer.
B .............................................................. are used in electronic circuits and come in many
different types and applications. Electronics or power transformers are sometimes considered
to be those with ratings of 300 volt-amperes and below. These transformers normally provide
power to the power supply of an electronic device, such as in power amplifiers in audio
receivers.
C .............................................................. are generally used in electronic circuits that require
constant voltage or constant current with a low power or volt-amp rating. Various filtering
devices, such as capacitors, are used to minimize the variations in the output. This results in a
more constant voltage or current.
D The ....................................................... is generally used in low power applications where a
variable voltage is required. The auto transformer is a special type of power transformer. It
consists of only one winding. By tapping or connecting at certain points along the winding,
different voltages can be obtained (Figure 8).
Figure 8 ................................................... Schematic
By Justyna Plezia and Magdalena Potręć (AGH UST)
For classroom use at AGH UST . You can distribute the copies in paper and electronic form among fellow teachers and second cycle
students at AGH UST only. Some sections may contain copyrighted material and can be used for educational purposes only and cannot
be made publicly available.
3
E .............................................................. are normally low power transformers used to isolate
noise from or to ground electronic circuits. Since a transformer cannot pass DC voltage from
primary to secondary, any DC voltage (such as noise) cannot be passed, and the transformer
acts to isolate this noise.
F The ....................................................... (PT) steps down voltage of a circuit to a low value
that can be effectively and safely used for operation of instruments such as ammeters,
voltmeters, watt meters, and relays used for various protective purposes.
G The ...................................................... (CT) steps down the current of a circuit to a lower
value and is used in the same types of equipment as a potential transformer. This is done by
constructing the secondary coil consisting of many turns of wire, around the primary coil,
which contains only a few turns of wire. In this manner, measurements of high values of
current can be obtained. A current transformer should always be short-circuited when not
connected to an external load. Because the magnetic circuit of a current transformer is
designed for low magnetizing current when under load, this large increase in magnetizing
current will build up a large flux in the magnetic circuit and cause the transformer to act as a
step-up transformer, inducing an excessively high voltage in the secondary when under no
load.
Adapted from http://www.tpub.com
b) Complete the expressions with appropriate prepositions. What other prepositions can be
used?
1.
2.
3.
4.
5.
6.
7.
differences
relationship
designated
used
result
consist
isolate
…………
…………
………....
………....
…………
………....
………....
c) Find words in the text which match the following definitions.
1. ………………………….. – the rate at which a device converts electrical energy into
another form of energy, such as light, heat, or motion or maximum power to be used
with that device (par. A)
2. ………………………… material – material which allows heat to go through (par. A)
3. …………………………. – a piece of equipment that changes radio and television
signals into sounds and pictures (par. B)
4. …………………………. – a device which collects and stores electricity (Par. C)
5. …………………………. – an amount of something produced by a person, machine,
factory, country, etc (par. C)
6. …………………………. – a conducting connection between an electric circuit or
equipment and the earth or some other conducting body (par. E)
7. …………………………. – a device that reacts to a small change in an electrical
current by moving switches or other devices in an electrical circuit (par. F)
8. …………………………. – giving protection (par. F)
9. …………………………. – continuous change (par. G)
By Justyna Plezia and Magdalena Potręć (AGH UST)
For classroom use at AGH UST . You can distribute the copies in paper and electronic form among fellow teachers and second cycle
students at AGH UST only. Some sections may contain copyrighted material and can be used for educational purposes only and cannot
be made publicly available.
4
d) Now complete the following sentences with expressions from part a)
1. It comprises a transmitter and a portable ………………………… which is designed
to be moved from one location to another as required.
2. A …………………..ed wire on a lightning rod leads large electric charges from the
atmosphere directly to Earth, preventing them from taking other paths that might
result in damage to property or injury to persons.
3. If several powerheads are being used, they should all be of the same make and
…………………………… to provide maximum efficiency.
4. Ramtron aims in future to actually replace the …………………….. with a small
amount of ceramic embedded in the chip.
5. The BBC has always maintained that it needs more spectrum for each service to be
able to provide more …………………. stations in remote areas.
6. Researchers will present this ……………………… plastic at the Composites trade
fair in October.
7. Our plans are in a state of ……………….. at the moment.
8. Last year British manufacturing …………………. fell by 14%.
9. The crash crew person had to don the …………………….. clothing after arriving at
the scene.
Task 5
Write three questions based on the text to check your partner’s comprehension.
1. ...................................................................................................
2. ...................................................................................................
3. ...................................................................................................
Task 6
Watch the video about ABB transformers presenting the process of design and construction
and complete the sentences with appropriate words and phrases.
1. Transformer designers …………………………. the important data.
2. The core is made up of ………………. laminations.
3. The highest level of precision is guaranteed because of ..............................................
……………............. of sheets
4. For the windings the manufacturers use insulated electrolytic ……………………
…………….
5. Factors taken into account during production are ……………………….. ,
……………… expectations and electric and …………………………….. .
6. During the work any kind of ……………………………. should be avoided.
7. Drying process is crucial as ……..……………………………. may deteriorate
performance.
8. Tank designs are affected by such factors as the ……………………………… ,
……………… …………………. and ……………………………………….
9. Weld testing usually includes: …………………….., ………………….. and ultrasonic
……………………………..
10. Manufacturing process can be accommodated to special ........................................
…………………., such as cooling
systems, ............................, .................................., ............................................... onload tab changers and ...............................................
By Justyna Plezia and Magdalena Potręć (AGH UST)
For classroom use at AGH UST . You can distribute the copies in paper and electronic form among fellow teachers and second cycle
students at AGH UST only. Some sections may contain copyrighted material and can be used for educational purposes only and cannot
be made publicly available.
5
11. Transformers can be tested in following types of tests:
- …………………….. and switching impact test
- induced ………………………….tests
- ………………………………….. tests.
Recording from http://www.youtube.com/
Task 7
Match the words in column A with the words from column B to create whole phrases and
translate the phases into Polish.
expressions with verbs
A
1. to evaluate
2. to take
3. to jeopardize
4. to meet
5. to subcontract out
6. to exercise
7. to accommodate
expressions with adjectives
A
1. tailor2. highly3. cost4. closely5. stringing
6. on-
a)
b)
c)
d)
e)
f)
g)
B
special customer requirements
responsibility
relevant data
transformer performance
requirements
work
precautions to avoid sth
a)
b)
c)
d)
e)
f)
B
overseen
efficient
made designs
standards
site test
trained staff
By Justyna Plezia and Magdalena Potręć (AGH UST)
For classroom use at AGH UST . You can distribute the copies in paper and electronic form among fellow teachers and second cycle
students at AGH UST only. Some sections may contain copyrighted material and can be used for educational purposes only and cannot
be made publicly available.
6