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.
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.
TASK 9. 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, …, …, … on load tab changers and …. 11. Transformers can be tested in following types of tests: … and switching impact test; induced …tests; … tests.
TASK 10. Match the words in column A with the words from column B to create whole phrases.
Expressions with verbs:
| 1. to evaluate 2. to take 3. to jeopardize 4. to meet 5. to subcontract out 6. to exercise 7. to accommodate | a) special customer requirements b) responsibility c) relevant data d) transformer performance e) requirements f) work g) precautions to avoid smth |
Expressions with adjectives:
| 1. tailor- 2. highly- 3. cost- 4. closely- 5. stringing 6. on | a)overseen b) efficient c) made designs d) standards e) site test f) trained staff |
UNIT 12
Task 1. Match the words and phrases with the translations.
| 1. | amplifier | a | доставлять | |
| 2. | respond to | b | характеристика | |
| 3. | input signal | c | твердотельная микросхема | |
| 4. | deliver | d | удовлетворительный | |
| 5. | output signal | e | употреблять, применять | |
| 6. | waveform | f | общий | |
| 7. | feature | g | вовлекать, включать в себя | |
| 8. | receiver | h | реагировать | |
| 9. | high-fidelity | i | подавать (питание), передавать | |
| 10. | employ | j | этап | |
| 11. | solid-state microcircuit | k | приемник | |
| 12. | raise | l | соединение (в пару) | |
| 13. | level | m | усилитель | |
| 14. | feed into | n | многоступенчатый | |
| 15. | satisfactory | o | усиление | |
| 16. | multistage | p | форма сигнала (волны) | |
| 17. | overall | q | увеличивать | |
| 18. | gain | r | входной сигнал | |
| 19. | coupling | s | поднимать, увеличивать | |
| 20. | involve | t | высокоточный | |
| 21. | successive | u | помехи | |
| 22. | stage | v | последовательный | |
| 23. | magnify | w | выходной сигнал | |
| 24. | distortion | x | уровень |
TASK 2. Read the text about amplifiers and complete it with the words and phrases.
| output signal, amplifier, receivers, responds to, high-fidelity, input signal, delivers, waveform, employ |
1) … is a device that 2) … a small input signal (voltage, current, or power) and 3) … a larger 4) … that contains the essential 5) … features of the 6) …. Amplifiers of various types are widely used in such electronic equipment as radio and television 7) …, 8) … audio equipment, and computers. Amplifying action can be provided by electromechanical devices (e.g., transformers and generators) and vacuum tubes, but most electronic systems now 9) … solid-state microcircuits as amplifiers. Such an integrated circuit consists of many thousands of transistors and related devices on a single tiny silicon chip.
| multistage, gains, to raise, overall, satisfactory, level, fed into |
A single amplifier is usually not enough 10) … the output to the desired 11) …. In such cases the output of the first amplifier is 12) … a second, whose output is fed to a third, and so on, until the output level is 13) …. The result is cascade, or 14) … amplification. Long-distance telephone, radio, television, electronic control and measuring instruments, radar, and countless other devices all depend on this basic process of amplification. The 15) … amplification of a multistage amplifier is the product of the 16) … of the individual stages.
| successive, coupling, solid-state, involved, stages |
There are various schemes for the 17) … of cascading electronic amplifiers, depending upon the nature of the signal 18) … in the amplification process. 19) … microcircuits are better than vacuum-tube circuits for the direct coupling of 20) … amplifier 21) …. Transformers can be used for coupling, but they are too big and expensive.
| distortion, magnified |
An electronic amplifier can be designed to produce a 22) … output signal identical in every respect to the input signal. This is linear operation. If the output is altered in shape after passing through the amplifier, amplitude 23) … exists. If the amplifier does not amplify equally at all frequencies, the result is called frequency distortion, or discrimination.
task 3. Answer the questions below and retell the text.
1. What is the main purpose of the amplifier? 2. Where are amplifiers used? 3. What electromechanical devices are used to provide the amplification of the input signals? 4. What can be done in case if the single amplifier is not enough to get a desired level of signal? 5. What are the examples of devices which depend on the multistage amplification? 6. What is the overall amplification of the multistage amplifier due to? 7. Why are microcircuits better for coupling than transformers? 8. What causes amplitude distortion?
TASK 4. Match the names with the descriptions.
Current amplifier