Урок 2. Unit 2.

1. Прочитайте следующие слова, обращая внимание на чтение

подчеркнутых согласных букв и буквосочетаний.

considering circuit surroundings flux

current since flows maximum

circuit cycle size explain

magnetic sine increasing basics

can certain opposes excess

cycle resistance resistive mixing

cause same zero express

peak receive rise exchange

check loss degrees axial

efficiency direction which voltage

accomplish alternation will device

shape situation wave value

ratio operation where wave

potential induction would voltmeter

tertiary connection when relative

establish section wire subdivision

pressure transmission wound very

should proportion winding divide

behind change equip magnetic

hinder actually equipment magnitude

have reach equal lag

high check require degree

handle mutual equivalent regard

who combustion quick figure

whose feature square together

whole structure quality negative

whom manufacture quantity language

voltage both then alternating

large something there surrounding

energy third that single

energize through they bank

generator nothing this winding

damage method these metering

injury strength another relaying

adjustable thick within readings

change mathematics without strength

2. Прочитайте и запомните следующие слова и словосочетания:

an alternating current circuit – цепь переменного тока;

a magnetic field – магнитное поле;

inductance – индуктивность; самоиндукция, собственная индукция;

both the current and the voltage – и ток, и напряжение;

magnitude – амплитуда;

to lag behind – отставать, запаздывать;

an induction motor – асинхронный двигатель;

a transformer – трансформатор;

a reactor – (электрический) реактор; катушка индуктивности;

to energize – включить(подать) напряжение; возбудить;

to de-energize – отключать, снимать напряжение; обесточивать; снимать

возбуждение;

a collapsing field – (зд.) перенапряжение

to flash over – вспыхивать; искрить;

a circuit breaker – автоматический выключатель;

a field breaker – автомат гашения поля;

a coil – катушка (индуктивности);секция обмотки (катушки); намотка;

обмотка;

a turn – виток; оборот;

spacing – расстояние; интервал; промежуток;

a winding – обмотка;

power operations personnel – оперативный персонал;

to transfer power – переносить; передавать энергию;

a core – сердечник; стержень;

mutual inductance – взаимная индукция;

self-inductance – собственная индуктивность, самоиндукция;

3. Прочитайте текст 2. “Inductance”, подчеркните во всех

предложениях подлежащее, сказуемое, определения. Укажите грамматическую модель каждого предложения. Назовите формальные признаки, по которым можно определить временные формы глагола-сказуемого.

TEXT 2. INDUCTANCE

In considering alternating current circuits, remember anytime current flows, a magnetic field surrounds the conductor. That flux (magnetic field) surrounding it is relative to the direction of current flow in the conductor. Since the alternating current circuit entails the alternation of the current flow first in one direction and then in another, the flux is also increasing and decreasing. As the current flow changes direction, the direction of the flux surrounding that conductor also changes.

In order to fully understand alternating current circuits we’ll consider certain other phenomena. The first of which we will term inductance. Inductance is the property of an electrical circuit which opposes the change of current. In an alternating current circuit both the current and the voltage alternate in magnitude and polarity (direction). Since the current and voltage alternate, the phenomenon of inductance retards the rate at which the current can change. It does not hinder the changing of the voltage. In a 60 (sixty) cycle system, if there is inductance in a circuit, the inductance actually retards and causes the current to lag behind the voltage sine wave.

In simple terms, the effect of inductance upon an AC circuit is that the inductance retards the current sine waves and causes them to lag behind the voltage sine waves. If there is no inductance in a circuit and it is purely resistive, the current and the voltage change at the same rate. They reach maximum at the same time and they reach zero at the same time. When inductance is introduced into a circuit, the inductance causes the current sine wave to lag behind that of the voltage sine wave. When inductance is introduced into a circuit, the current and the voltage do not rise to maximum at the same time, nor do they fall to zero at the same time. They peak and reach zero at different times. A complete cycle is said to be 360 electrical degrees.

The maximum amount that inductance can cause current to lag behind the voltage would be 90 (ninety) electrical degrees. This is evident in any electrical circuit where there is a large number of induction motors. A large size or number of induction motors, transformers, reactors or other equipment which introduces inductance into an electrical circuit causes the current to lag behind the voltage.

Any time the current and the voltage do not peak at the same time, there is a loss of efficiency. This means that it requires more current to do the same amount of work as would have previously been accomplished if the current and the voltage were both in phase. The efficiency of the equipment operation is less if the current and the voltage do not peak or reach zero at the same time.

Inductance in a direct current (DC) circuit is significant when there is a great increase or decrease of current flow in that circuit and upon energizing or de-energizing that circuit. When a DC system is de-energized rapidly the collapsing field in the DC circuit produces a very high induced voltage. This induced voltage is relative to the rate at which the lines force collapse and to the strength of the magnetic field. Actually this can be so great in magnitude as to “flash over” certain pieces of equipment. This induced voltage in a situation like this can be many times that of the normal circuit voltage. This may be evidenced on the opening of the generator field breakers.

Inductance of a circuit is measured in units of measurement termed “Henries”. A “Henry” is used to measure the inductance of a coil. Inductance can not be measured in ohms. A simple resistor can be checked with an ohmmeter. The inductance of a circuit is dependent on a number of factors. It is dependent upon the number of turns, the spacing between the turns, the shape of the coils, the diameter of the coil, the core material, the wire size, the number of layers of windings and the manner in which it is wound. Each of these things is involved in determining the inductance of a circuit. The calculation of the circuit inductance is something which is not ordinarily calculated by power operations personnel. However, inductance is a very important factor with regard to the operation of power systems. The operation of transformers is directly attributable to inductance.

Inductance is the ability to transfer power from one conductor to another conductor without a direct electrical connection. In a transformer, two conductors are wound around a common core. Because the flux is rapidly expanding at the rate of 60 cycles per second, inductance is present between the two coils. The secondary winding of the transformer has a voltage induced therein. If the secondary circuit is completed, current will flow.

Energy can be transferred from one circuit to the other by induction. This is commonly termed mutual induction. That is a transfer of power or voltage from one circuit to the other without a direct electrical connection. Self-inductance is another term which refers to the induction within one circuit.

3. Переведите следующие словосочетания на русский язык,

применяя правило “цепочки существительных”:

1. alternating current circuits

2. a current flow

3. a voltage sine wave

4. an induction motor

5. equipment operation

6. generator field breakers

7. the circuit voltage

8. the core material

9. the wire size

10) the circuit inductance

11) power operations personnel

12) power systems

3. Подберите русские эквиваленты к следующим английским

словам:.

field flux current circuit voltage degree equipment magnitude breaker 10) turn 11) core 12) winding 13) coil 14) conductor 15) transfer

1) амплитуда 2) сердечник 3) передача 4) поле 5) проводник 6) обмотка 7) оборудование 8) магнитный поток 9) виток 10) градус 11) напряжение 12) цепь, контур 13) выключатель, прерыватель 14) электрический ток 15) катушка

3. Найдите в тексте английские эквиваленты следующим русским

фразам:

1. при рассмотрении, рассматривая;

2. всякий раз, когда;

3) связан, соответствует, соотносится с;

3. для того, чтобы полностью понять;

4. фактически (действительно) замедляет, задерживает, тормозит;

5. проще говоря;

6. с одной и той же скоростью;

7. известно, что полный цикл составляет;

8. это означает, что;

9. требуется больше тока, чтобы;

10. измеряется в единицах;

11. ряд факторов;

12. то, что обычно не;

13. напрямую (прямо) приписывается, обусловлено;

14. поскольку поток быстро расширяется;

15. то есть передача.

3. Найдите в тексте информацию и расскажите о явлении

индуктивности и единицах ее измерения.

3. Переведите текст на русский язык.