电气工程及其自动化专业英语
Specialized English for Electrical
Engineering ＆ Its Automation
戴文进 主 编
杨植新 副主编
Contents
• Part 1
Electrics and Electronics
• Part 2
Electric Machinery
• Part 3
Electrical Engineering
• Part 4 Modern Computer Control
Techniques
Unit 1 Specialized English Words
circuit components 电路元件
circuit parameters 电路参数
the dielectric 电介质
storage battery 蓄电池
electric circuit 电路
wire导线
electrical device 电气设备
electric energy 电能
energy source 电源
primary cell 原生电池
secondary cell 再生电池
energy converter 电能转换器
e.m.f.＝electromotive force 电动势 unidirectional current 单方向电流
circuit diagram 电路图
load characteristic 负载特性
terminal voltage 端电压
external characteristic 外特性
Conductor 导体
load resistance 负载电阻
generator 发电机
heating appliance 电热器
direct-current(D.C.) circuit 直流电路 magnetic and electric field 电磁场
time-invariant 时不变的
self-(or mutual-)induction 自（互）感
displacement current 位移电流
voltage drop 电压降
conductance 电导
volt-ampere characteristics 伏安特性
metal-filament lamp 金属丝灯泡
carbon-filament lamp 碳丝灯泡
non-linear characteristics 非线性特性
Unit 1 Circuit Elements and Parameters
• An electric circuit (or network) is an interconnection of
physical electrical devices. The purpose of electric circuits is
to distribute and convert energy into some other forms.
Accordingly, the basic circuit components are an energy
source (or sources), an energy converter (or converters) and
conductors connecting them（连接它们的）.
• An energy source (a primary or secondary cell, a generator
and the like) converts chemical, mechanical, thermal or
some other forms of energy into （将---转换成---）electric
energy. An energy converter, also called load (such as a
lamp, heating appliance or electric motor), converts electric
energy into light, heat, mechanical work and so on.
• Events in a circuit can be defined in terms of （用---，根据---）
e.m.f. (or voltage) and current. When electric energy is
generated, transmitted and converted under conditions such
that the currents and voltages involved remain constant with
time, one usually speaks of direct-current (D.C.) circuits.
• With time-invariant currents and voltages, the magnetic and
electric fields of the associated electric plant are also timeinvariant. This is the reason why no e.m.f.s of self- (or
mutual-)induction（自感或互感）appear in D.C. circuits, nor
are there （倒装结构）any displacement currents （位移电
流）in the dielectric surrounding the conductors(导体周围的
电介质）.
• Fig.1.1 shows in simplified form a hypothetical circuit with a
storage battery as the source and a lamp as the load. The
terminals of the source and load are interconnected by
conductors (generally but not always wires). As is seen, the
source, load and conductors form a closed conducting path.
The e.m.f. of the source causes a continuous and
unidirectional current to circulate round this closed path.
• This simple circuit made up of
a source, a load and two wires is
seldom, if ever, met with in practice.
Practical circuits may contain a large
number of sources and loads
interconnected in a variety of ways
（按不同方式连接的）.
Fig.1.1
• To simplify analysis of actual circuits, it is usual to show
them symbolically in a diagram called a circuit diagram,
which is in fact a fictitious or, rather, idealized model of an
actual circuit of network.
Such a diagram consists of
interconnected symbols called
circuit elements or circuit
parameters. Two elements are
necessary to represent
processes in a D.C. circuit.
These are a source of e.m.f. E
and of internal (or source)
resistance RS, and the load
resistance (which includes the
resistance of the conductors) R (Fig.1.2)
Fig.1.2
• Whatever its origin (thermal, contact, etc.), the source e.m.f. E
(Fig.1.2 (a)) is numerically equal to the potential difference
between terminals 1 and 2 with the external circuit open, that
is, when there is no current flowing through the source
E = ϕ1 − ϕ 2 =V12
(1.1)
The source e.m.f. is directed from the terminal at a lower
potential to that （代替terminal） at a higher one（代替
potential）. On diagram, this is shown by arrows（箭头）.
• When a load is connected to the source terminals (the circuit
is then said to be loaded) and the circuit is closed, a current
begins to flow round it. Now the voltage between source
terminals 1 and 2 (called the terminal voltage) is not equal to
its e.m.f. because of the voltage drop VS inside the source,
that is, across the source resistance RS
VS=RSI
• Fig.1.3 shows a typical so-called external
characteristic V = ϕ1 − ϕ 2 =V(I) of a
loaded source (hence another name is
the load characteristic of a source). As is
seen, increase of current from zero to
I≈I1 causes the terminal voltage of the
source to decrease linearly
V12=V=E－VS=E－RSI
Fig.1.3
In other words, the voltage drop VS across the source
resistance rises in proportion to the current. This goes on until
a certain limit is reached. Then as the current keeps rising, the
proportionality between its value and the voltage drop across
the source is upset, and the external characteristic ceases to
be （不再是）linear. This decrease in voltage may be caused
by a reduction in the source voltage, by an increase in the
internal resistance, or both.
The power delivered by a source is given by the equality（等式）
PS=EI
(1.2)
where PS is the power of the source.
• It seems relevant at this point to dispel a common
misconception about power. Thus one may hear that power is
generated, delivered, consumed, transmitted, lost, etc. In point
of fact, however, it is energy that can be generated, delivered,
consumed, transmitted or lost. Power is just the rate of energy
input or conversion, that is, the quantity of energy generated,
delivered, transmitted etc per unit time. So, it would be more
correct to use the term energy instead of power in the above
context. Yet, we would rather fall in with the tradition.
• The load resistance R as a generalized circuit element, gives
an idea about the consumption of energy, that is ,the
conversion of electric energy into heat, and is defined as
P=RI2
(1.3 )
In the general case, the load resistance depends solely on the
current through the load, which in fact is symbolized by（用符
号） the function R(I).
• By Ohm\s law, the voltage across a resistance is
V=RI
(1.4)
• In circuit analysis, use is often made of the reciprocal of
the resistance, termed the conductance, which is defined as
g = 1/ R
In practical problems, one often specifies the voltage
across a resistance as a function of current V(I), or the
inverse relation I(V) have come to be known as volt-ampere
characteristics.
• Fig.1.4 shows volt-ampere
curves for a metal-filament
lamp V1(I), and for a carbonfilament lamp V2(I). As is seen,
the relation between the
voltage and the current in each
lamp is other than linear. The
resistance of the metalfilament lamp increases, and
that of the carbon-filament
lamp decreases with increase
of current.
Fig.1.4
•Electric circuits containing components with non-linear
characteristic （含有非线性特性元件的）are called non-linear.
• If the e.m.f. and internal resistances
of sources and associated load
resistances are assumed to be
independent of the current and
voltage, respectively, the external
characteristic V(I) of the sources
and the volt-ampere characteristic
V1(I) of the loads will be linear.
• Electric circuits containing only
elements with linear characteristic
are called linear.
Fig.1.5
of interest=interesting
Most practical circuits may be classed as linear.
Therefore, a study into the properties and analysis of linear
circuits is of both theoretical and applied interest.
Unit 2 Specialized English Words
• ideal source
理想电源
• series and parallel equivalent circuit
• internal resistance
内阻
串并联等值电路
double subscript
双下标
ideal voltage source 理想电压源
active circuit elements有源电路元件
•
passive circuit elements
无源电路元件
•
power transmission line
输电线
•
sending end
•
leakage current
发送端
receiving end
漏电流 ideal current source
接收端
理想电流源
Unit 2 Ideal Sources Series and Parallel
Equivalent Circuits
• Consider an elementary circuit containing a single source of
e.m.f. E and of internal resistance RS, and a single load R
(Fig.2.1). The resistance of the conductors of this type of
circuit may be neglected. In the external portion of the circuit,
that is, in the load R, the current is assumed to flow from the
junction a (which is at a higher potential such that ϕ a = ϕ1 )
to the junction b (which is at a lower potential such that ϕ b =
ϕ 2 ). The direction of current flow may be shown either by a
hollow arrowhead or by supplying the current symbol with a
double subscript whose first digit identifies the junction at a
higher potential and the second (省略了identifies) the
junction at a lower potential. Thus for the circuit of Fig.2.1,
the current I=Iab .
We shall show that the circuit of Fig.2.1
containing a source of known e.m.f. E and
source resistance R may be represented
by two types of equivalent circuits.
As already started, the terminal voltage
of a loaded source is lower than the
source e.m.f. by an amount equal to the
voltage drop across the source resistance
Fig.2.1
V = ϕ1 − ϕ 2 = E −VS = E − RSI
(2.1)
On the other hand, the voltage across
the load resistance R is
V = ϕ a − ϕ b = RI
(2.2)
Since ϕ 1 = ϕ a and ϕ 2 = ϕ b , from Eqs.(2.1) and (2.2) it
follows that E-RsI=RI, or
E=RSI+RI
(2.3)
And
I=E/ (RS+R)
• From the last equation we conclude that the current through
the source is controlled by both the load resistance and the
source resistance. Therefore, in an equivalent circuit diagram
the source resistance R may be shown connected in series
with （与---串联） the load resistance R. This configuration
may be called the series equivalent circuit (usually known as
the Thevenin equivalent source---戴维宁等效电源).
• Depending on the relative
magnitude of the voltages
across Rs and R, we can
develop two modifications
of the series equivalent
circuit（串联等效电路）.
Fig.2.2
• In the equivalent circuit of Fig.2.2(a), V is controlled by the
load current and is decided by the difference between the
source e.m.f. E and the voltage drop V.
If RS<<R and, for the same current, VS<<V (that is, if the
source is operating under conditions very close to（接近）
no-load or an open-circuit), we may neglect the internal
voltage drop, put VS=RI=0 (very nearly) and obtain the
equivalent circuit of Fig.2.2(b).
What we have got is a source whose internal resistance is
zero (R=0). It is called an ideal voltage source. In diagrams
it is symbolized by （用---符号表示）a circle with (with结
构）an arrow inside and the letter E beside it. When
applied to a network, it is called a driving force or an
impressed voltage source.
The terminal voltage （端电压）of an ideal voltage source is
independent of the load resistance and is always equal to the
e.m.f. E of the practical source it represents. Its external
characteristic is a straight line parallel to the x-axis（与X轴平行
的） (the dotted line ab in Fig.1.3). The other equivalent circuit
in Fig.2.3 may be called the parallel equivalent circuit (usually
known as the Norton equivalent---诺顿等效电路). It may also
have two modifications. To prove this, we divide the right- and
left-hand sides of Eq.(2.3) by RS
E/RS=I+V/RS=I+VgS or
J=I+IS (2.4)
where J=E/RS ,current with the source short-circuited (with R=0);
• IS=V/RS=VgS ------- current equal to the ratio of the terminal
source voltage to the source resistance（---与---的比率）;
• I=V/R=Vg ------- load current.
• Eq.(2.4) is satisfied by the
equivalent circuit of Fig.2.3(a) in
which the source resistance RS
is placed in parallel with （与--并联）the load resistance R.
Fig.2.3
• If gS<<g or RS>>R and, for the What we have got is a source
same voltages across RS and R, of zero internal conductance,
gS=0(RS=∞). It is called an
the current IS<<I (that is, if the
ideal current source. When
source is operating under
applied to a circuit, it is called a
conditions approaching a short- driving force of an impressed
current source.
circuit), we may put IS=VgS=0
The current of an ideal current
(very nearly) and get the
source is independent of the
equivalent circuit of Fig.2.3(b).
load resistance R and is equal
to E/RS.
• The external characteristic of an ideal current source is a
straight line parallel to the y-axis （平行于Y轴的）(the
dotted line cd in Fig.1.3).
• Thus whether a real energy source may be represented by
an ideal voltage source or an ideal current source depends
on the relative magnitude of RS and R. A real source, though,
may be represented by an ideal voltage or current source
also when RS is comparable with R. In such a case, either RS,
or gS=1/RS (Fig.2.2 (a) and Fig.2.3(a), respectively) should
be removed from the source and lumped with R or g=1/R.
• Ideal voltage and current sources are active circuit elements
（有源电路元件）, while resistances and conductance are
passive elements(无源元件）.
• In developing an equivalent circuit, it is important to take into
account, as much as practicable（实际上）,the known
properties （已知的特性）of each device and of the circuit as
a whole（整体上）.
• Let us develop an equivalent circuit for a two-wire power
transmission line （输电线）of length I, diagrammatically
shown（用图形表示） in Fig.2.4 (a). There is a generator of
e.m.f.E and of source resistance RS at the
sending end and a
load of resistance R2
at the receiving end
of the line.
Fig.2.4
• It is obvious that the receiving end voltage will be less than
the sending end one by an amount equal to the voltage
drop across the resistance of the line conductors. The
current at the receiving end will be smaller than that at the
sending end by an amount equal to the leakage current
（漏电流）(due to imperfect insulation---绝缘不完善).
• A less than B by an amount (which is) equal to ------;
A比B少--• Let each line conductor have a resistance R0/2 and a
conductance g0 per unit length of the line. We divide the
line into length elements dx (Fig.2.4(a)). Then each length
element will have associated with it the combined
resistance of the “go” and “return” wires,
R0dx=(R0/2)dx+(R0/2)dx and a conductance g0dx（这样，
一长度元将含有与其相关的、含有‘去’与‘来’两段组合
的电阻即 R0dx＝(R0/2)dx+(R0/2)dx）和电导 g0dx ）.
• Accordingly, the entire line may be represented by a
network of elements each of resistance R0dx and
conductance g0dx (Fig.2.4 (b)). The sending end generator in
this network is represented by a voltage source (of e.m.f. E
and of source resistance RS).
• From this equivalent circuit we can find （计算出） the
voltage and current at any point on the line in terms of
specified voltage and current （根据给定的电压和电流）at
the sending or receiving end. If the leakage current of the line
is only a small fraction of （只占小部分）the load current, we
may neglect it and remove all conductance g0dx from the
network（把所有的电导从网络中移开）.
This will leave us with a simple, single-loop network with one
and the same current in each of its elements, such as shown
in Fig.2.5, where the line resistance Rline=R0l is connected in
series with RS and R2. The network of Fig.2.5 may be used
for analysis of line performance without a consideration of
（不考虑） leakage currents（漏电流）.
Fig.2.5
• It takes some practiceto learn to develop equivalent circuits
such as will reflect the behavior of physical prototypes in
the most faithful manner and meet the requirements of
the problem at hand（遇到的）
• 此句的主句是 It takes some practice to learn to develop
equivalent circuits, 其中to learn to develop equivalent
circuits 是不定式短语做主语，只是由于其太长，若放在句首
会给人头重脚轻的感觉。 其次要了解此句是“It takes
something（time, money）”的句型，此处 practice的意思是
“要花一些时间（实践），要花一些工夫的”。即“要学会画
（这样的）等值电路是要花一番工夫的。”那么是什么样的等
值电路呢？后面整个都是由 such as (that)引导的定语从句，
修饰 equivalent circuits,意为“既能以最可靠的方式反映实际
电路的运行情况，又能满足常常遇到的实际问题需要的这样一
种等值电路”。
Unit 4 Alternating current
Specialized English Words
alternating current 交流电
definition 定义
instant of time 瞬时
frequency 频率
instantaneous value of current 电流瞬时值
symbolized by 用符号表示
harmonic (or sinusoidal)
current 正弦电流
over-voltage 过电压
communication circuit 通信电路
remote control 遥控
period 周期
modulated by（由U）调制
periodic current 周期电流
pole-pairs 极对数
non-salient pole 隐（非凸）极
mechanical strength 机械强度
heat-treatment 热处理
induction-heating 感应发热
peak value （交变量的）最大值
semiconductor oscillator 半导体振荡器
amplitude （交变量的）幅值
phase 相位
initial phase 初相位
epoch angle 初相角
pulsatance 谐振常数角频率 angular velocity 角频率
in quadrature 正交
A.C. generator 交流发电机
stator （电机）定子
magnetic pole 磁极
rotor （电机）转子
slip-ring 滑环
slot 槽
stacked up 叠装
electrical-sheet steel 电工钢片
magnetic induction 磁感应强度
active length 有效长度
distribution of B 磁场分布
phase shift＝phase displacement 相位移
lag in phase behind （相位）落后
in phase 同相
anti-phase 反相
Unit 4 Alternating Current
Basic Definitions
• An alternating current is one which varies in the circuit with
time（随时间变化）. The value of the current at any given
instant of time is termed （called）the instantaneous value
of current, symbolized by i. The instantaneous value of
current i is deemed （认为是）positive for one direction of
flow through the cross-section of a conductor, and negative
for the opposite direction（省略了成分）. A current is fully
specified, if one knows its instantaneous values as a function
of time, i=F(t), and its positive direction.
• Currents whose values recur for equal increments of time
are called periodic, and the least increment of time for which
this recurrence takes place is called the period T. For a
periodic current i=F(t)=F(t+T)
• Fig.4.1 shows an example of the relationship i=F(t) for a
periodic current. The arrow in the diagram indicates the
positive direction of current flow（电流正方向）. The dotted
arrows show the actual directions of current flow at the
instants of time when i>0 and i<0. The segments of the curve
between points a and b or O and c cover a complete cycle of
current alternations over one period.
The number of cycles or periods per
second is the frequency of a periodic
current. It is reciprocal of its period
f =1/T
It is usually to specify the frequency of
any periodic quantity in cycles per
second（每秒周数）. Thus the
frequency of a periodic current will be
1 cycle per second, if its period is 1
second, or 1 cycle/sec.
Fig.4.1
• A direct current may be regarded as a special case of a
periodic current whose period is infinitely long（无穷大） and
the frequency is thus zero.
• The term（术语） alternating current is often used in the
narrow sense of a periodic current whose constant (directcurrent) component is zero, or
1 T
idt  0
T 0
• The frequencies of alternating current encountered in
practice （在实际中遇到的）range over （涉及）very wide
values. The mains frequency is 50Hz in the Soviet Union and
Europe, and 60Hz in the United States. Some industrial
processes use frequencies from 10 Hz to 2.5×109 Hz. in
radio practice（在无线电应用中）, frequencies up to
3×1010 Hz are employed.
• The definitions for currents just introduced (and, indeed,
those that will be introduced shortly) fully apply to periodic
voltages, e.m.f.s, magnetic fluxes and any other electrical
and magnetic quantities.Some additional remarks are only
needed with regard to the sign of alternating voltages and
e.m.f.s.
• An alternating voltage between two points A and B,
determined along a specified path l, periodically changes
sign, so that if it is assumed to be positive in the direction
from A to B（沿A到B的方向）, it will be negative in the
direction from B to A at the same instant of time【1】. This
is why it is important to label which of the two directions is
assumed positive. In diagrams, such a direction is labeled
either by arrows or subscripts in the symbols for voltages
and is regarded to be the positive reference direction of a
voltage (or of an e.m.f.).
• Electrical engineering uses the simplest and commonest
type of alternating current, the one which varies
sinusoidally with time; (按正弦规律变化）hence the term
（is called/termed）a harmonic or a sinusoidal current.
The preference for sinusoidal currents is explained by the
fact that non-sinusoidal currents entail increased energy
losses, induced over-voltages, and excessive interference
with （对---的干扰）communications circuits.
• The transmission of information over a distance (wire or
radio communications circuits, remote control, etc.) also
uses sinusoidal currents modulated by the signal in
amplitude, frequency or phase. Periodic non-sinusoidal
currents may likewise be treated as composed of
sinusoidal currents at a variety of frequencies occurring
simultaneously. This is why thorough of sinusoidal- current
circuits is of primary importance.
• The A.C. Generator
• An A.C. generator consists of a stationary part, the stator,
and a revolving part, the rotor. As a rule the rotor carries
magnetic poles with coils around them. These are the field
coils of the generator, because they establish a magnetic
field in the machine. They are energized with direct current
through slip rings and brushes. The slots of the stator
stacked up from electrical-sheet steel punchings receive
the coils of the stator winding【2】. The stator coils are
connected in series, as shown by the full and dotted lines
in the drawing.
• The e.m.f. induced in a stator conductor is given by E=Blv
• where B—magnetic induction of the field moving relative
to the conductor;
• l—active length of the conductor;
• v—speed with which the magnetic field moves relative to
the conductor.
• Since l and v are constant, the induced e.m.f.
will vary exactly as B varies. If the induced e.m.f.
is to be sinusoidal (which is usually sought), the
distribution of B around the circumference of the
stator should be as close to sinusoidal as
practicable.
• With p pole-pairs on the rotor, the e.m.f. will
undergo p cycles of changes every revolution. If
the speed of the rotor is revolutions per minute
(r/min), this works out to pn cycles per minute,
and the frequency of the induced e.m.f. is
f =pn/60
• For f =50Hz, the rotor of a generator with one
pair of poles should run at 3000 r/min. and
with two pole-pairs, at 1500 r/min. With
speeds like this, rotors are usually fabricated
with non-salient piles for greater mechanical
strength.
• High-frequency generators operating at 800
to 8000Hz are all of special designs. Their
uses are in the heat-treatment and inductionheating field. Still higher frequencies are
generated by valve and semiconductor
oscillators.
• Sinusoidal Current
• The instantaneous value of a sinusoidal current is given by
2
i

I
sin(
t )
m
•
(4.1)
T
2
(
• where Im is the peak value or amplitude of the current, and T t   )
is the phase of the current. The quantity ϕ is the initial phase
of the current (for t=0) and is termed the epoch angle. The
phase of a current continuously increases with time. When it
has increased by 2π, the whole cycle of changes is repeated
exactly all over again. Therefore, speaking of the phase of a
current, it is customary to drop the integer 2 π and to consider
the phase within ± π or between zero and 2 π.
The above change of phase by 2 π occurs during the period T.
therefore, the rate of change of the phase is given by 2 π /T. it
is symbolized by the Greek letter ω (omega) and is called the
pulsatance. Noting that f =1/T, we may write
ω =2 π /T=2 π f
(4.2)
• The above expression, relating ω and f, has been
responsible for the fact that the pulsatance ω is also
termed the angular velocity or frequency. It is expressed
in radians per second. Thus, for f =50 Hz, ù=314 rad/s.
Introducing ù in Eq.(4.1) we obtain I=Imsin(ù t+ ϕ )
• Sinusoidal currents of the same frequency, but differing
in amplitude and epoch angles, are shown in Fig.4.2.
Their instantaneous values are：
• i1= I m sin(ù t+ ϕ1 )
• i2= I m sin(ù t+ ϕ 2 )
• The time t or the product ω t,
proportional to time, is laid
off as abscissa.
Fig.4.2
• The epoch angle is always measured between the origin of
coordinates, which corresponds to the reference time t=0,
and the instant when a given sinusoidal quantity just passes
through zero (from negative to positive values). For ϕ1＞0,
the start (or zero point ) of the sinusoid i1 is shifted to the left,
and for ϕ2<0 it is shifted to the right of the origin of
coordinates（坐标原点）.
• Alternatively, the instantaneous value of a sinusoidal current
may be represented by a cosinusoidal function of the form
i=Imcos(ωt+ϕ) where ω =ϕ-π/2. When two or more sinusoidal
functions differ in time phase as reckoned from similar points,
they are said to be shifted or displaced in phase with respect
to （相对于）one another.
• This phase shift, or the phase displacement, is
measured between their respective zeros, and obviously
is the difference in epoch angles. Referring to Fig.4.3,
ϕ 1－ϕ2>0, and the current i1 is said to lead the current i2
in phase by ϕ 1－ϕ2, or, which is the same, the current i2
lags in phase behind the current i1 by ϕ 1－ϕ2.
• Two sinusoidal functions of the same frequency are said
to be in phase if they have same epoch angle, and are
said to be in anti-phase when
their phase displacement is
±π. Finally, they are said to
be in quadrature if their phase
difference is ± π/2.
Fig.4.3