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 way, so that the gap between 
the contacts can again withstand the voltage in the circuit. Different circuit 
breakers use vacuum, air, insulating gas, or oil as the medium in which the arc 
forms. 
Exercise 5: Are the following sentences true (T) or false (F)? 
1. All circuit breakers have common features in their operation, but details 
are not always the same. 
2. In low-voltage circuit breakers a fault condition is detected within the 
breaker enclosure. 
3. The only function of pilot devices is to sense a fault current. 
4. The trip solenoid that releases the latch is self-contained with current 
transformers, protection relays, and an internal control power source. 
5. Contacts within the circuit breaker must open to interrupt the circuit when 
some mechanically stored energy within the breaker is used to separate 
the contacts. 
6. The circuit breaker contacts must withstand the heat of the arc produced 
when interrupting the circuit. 
7. The erosion due to interrupting the arc limits the service life of the 
contacts. 
8. Miniature circuit breakers are usually replaced when the contacts are 
worn. 
9. When a current is interrupted, an arc is extinguished in a controlled way 
by the current. 
10. Vacuum, air, insulating gas, or oil can be used in different circuit 
breakers. 
Language work: Noun phrase (2) 
A noun phrase in English may take the following structure: 
Noun + Past Participle + Noun 
E.g: A hand operated valve 
The noun phrase ‘A hand operated valve’ means “a valve which is operated by 
hand” 
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Exercise 6 Now convert each of the following clauses into a noun phrase 
E.g: 
A valve which is operated by hand 
Æ a hand operated valve 
1. transformer which is cooled by air 
2. engineering which is aided by a computer 
3. switchgear which is insulated by gas 
4. end which is sprayed with metal 
5. valve which is operated by a motor 
6. screen which is coated with phosphor 
Exercise 7 Translate the noun phrases into Vietnamese 
E.g: hand operated valve (valve which is operated by hand) 
Æ van được thao tác bằng tay 
1. air-cooled transformer (transformer which is cooled by air) 
2. computer-aided enginnering (engineering which is aided by a computer) 
3. gas-insulated switchgear (switchgear which is insulated by gas) 
4. metal-sprayed end (metal sprayed end) 
5. motor-operated valve (valve which is operated by a motor) 
6. phosphor-coated screen (screen which is coated with phosphor) 
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 Unit 10 Rectifier 
Vocabulary and Pronunciation 
Exercise 1 Match English terms and Vietnamese translations 
English Vietnamese 
1. alternating current dạng sóng 
2. anode bộ chỉnh lưu, bộ nắn dòng 
3. arc dòng xoay chiều 
4. cathode chỉnh lưu cả sóng 
5. center-tapped hồ quang 
6. direct current phân cực, cực tính 
7. full-wave rectification cực dương 
8. half wave rectification nửa dương 
9. inverter đèn chân không 
10. negative half dòng một chiều 
11. polarity cực âm 
12. positive half nửa âm 
13. rectifier bộ đảo điện, bộ đảo lưu 
14. vacuum tube trích giữa 
15. waveform chỉnh lưu nửa sóng 
Exercise 2 T.S 1 Listen and practise 
1. alternating current 6. direct current 11. polarity 
2. anode 7. full-wave rectification 12. positive half 
3. arc 8. half wave rectification 13. rectifier 
4. cathode 9. inverter 14. vacuum tube 
5. center-tapped 10. negative half 15. waveform 
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Exercise 3 T.S 2 Listen and complete the sentences by selecting the correct 
word from the box to fill in the gap. 
alternating current direct current anode 
arc center-tapped rectifier 
cathode inverter vacuum tube 
1. A  transformer is a transformer with a tap in the middle of 
the secondary winding. 
2. An .. is an electrical device that converts  to 
. 
3. Some special function  are filled with low-pressure gas. 
4. An .. is an electrode through which electric current flows into a 
polarized electrical device. 
5. A  is an electrode through which electric current flows out of a 
polarized electrical device. 
listening: 
Exercise 4 Listen to T.S3 and fill in the blanks with the words given 
detectors convert diodes components arrangement
difference converts rectification development function 
A rectifier is an electrical device that (1)  alternating current (AC) 
to direct current (DC), a process known as (2) .. . Rectifiers have many 
uses including as components of power supplies and as (3) .. of radio 
signals. Rectifiers may be made of solid state diodes, vacuum tube diodes, 
mercury arc valves, and other (4) . . A device which performs the 
opposite (5) .. (converting DC to AC) is known as an inverter. When 
only one diode is used to rectify AC (by blocking the negative or positive 
portion of the waveform), the (6)  between the term diode and the 
term rectifier is merely one of usage, i.e., the term rectifier describes a diode 
that is being used to (7) .. AC to DC. Almost all rectifiers comprise 
a number of diodes in a specific (8)  for more efficiently converting 
AC to DC than is possible with only one diode. Before the (9)  of 
silicon semiconductor rectifiers, vacuum tube (10)  and copper(I) 
oxide or selenium rectifier stacks were used. 
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Reading 
Half-wave rectification
In half wave rectification, either the positive or negative half of the AC wave is 
passed, while the other half is blocked. Because only one half of the input 
waveform reaches the output, it is very inefficient if used for power transfer. 
Half-wave rectification can be achieved with a single diode in a one phase 
supply, or with three diodes in a three-phase supply. 
Full-wave rectification
A full-wave rectifier converts the whole of the input waveform to one of 
constant polarity (positive or negative) at its output. Full-wave rectification 
converts both polarities of the input waveform to DC (direct current), and is 
more efficient. However, in a circuit with a non-center tapped transformer, four 
diodes are required instead of the one needed for half-wave rectification. (See 
semiconductors, diode). Four rectifiers arranged this way are called a diode 
bridge or bridge rectifier: 
For single-phase AC, if the transformer is center-tapped, then two diodes back-
to-back (i.e. anodes-to-anode or cathode-to-cathode) form a full-wave rectifier 
(in this case, the voltage is half of that for the non-tapped bridge circuit above, 
and the diagram voltages are not to scale). 
A very common vacuum tube rectifier configuration contained one cathode and 
twin anodes inside a single envelope; in this way, the two diodes required only 
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one vacuum tube. The 5U4 and 5Y3 were popular examples of this 
configuration. 
Full-wave rectifier, with vacuum tube having two anodes. 
For three-phase AC, six diodes are used. Typically there are three pairs of 
diodes, each pair, though, is not the same kind of double diode that would be 
used for a full wave single-phase rectifier. Instead the pairs are in series (anode 
to cathode). Typically, commercially available double diodes have four 
terminals so the user can configure them as single-phase split supply use, for 
half a bridge, or for three-phase use. 
Exercise 5: Are the following sentences true (T) or false (F)? 
1. In half wave rectification, only one half of the AC wave is passed, while 
the other half is blocked. 
2. Half-wave rectification can only be achieved with a single diode in a one 
phase supply. 
3. Full-wave rectification converts both halves of the AC wave to DC. 
4. Full-wave rectification is more efficient than half-wave rectification. 
5. In half-wave rectification, more diodes are used than in full-wave 
rectification. 
6. A recfifier with a center-tapped transformer requires more diodes than a 
rectifier with a non-center tapped transformer. 
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7. A recfifier with a center-tapped transformer is more efficient than a 
rectifier with a non-center tapped transformer. 
8. A common vacuum tube rectifier configuration contained one anode and 
twin cathodes inside a single envelope. 
9. For three-phase AC, three pairs of diodes are used. 
Language work: Noun phrase (3) 
A noun phrase in English may take the following structure: 
Noun + Present Participle + Noun 
E.g: A current-carrying conductor 
The noun phrase ‘A current-carrying conductor’ means “a conductor which is 
carrying a current” 
Exercise 6 Now convert each of the following clauses into a noun phrase 
E.g: a conductor which is carrying a current 
Æ A current-carrying conductor 
1. radar which can find direction 
2. material which conducts current 
3. material which insulates heat 
4. device which can sense temperature 
5. pump which feeds oil 
6. system which processes data 
Exercise 7 Translate the noun phrase into Vietnamese 
A current-carrying conductor (a conductor which is carrying a current) 
Æ vật dẫn mang dòng 
1. direction finding radar (radar which can find direction) 
2. current conducting material (material which conducts current) 
3. heat insulating material (material which insulates heat) 
4. temperature sensing device (device which can sense temperature) 
5. oil feeding pump (pump which feeds oil) 
6. data processing system (which processes data) 
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REFERENCES 
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