-
1. Electrical Measuring
Instruments
电子测量仪表
Electrical personnel use many different
types of measuring instruments.
电子技术
人员使用许多不同类型的测量仪器。
Some
jobs
require
very
accurate
measurements
while
other jobs need only
rough estimates.
一些工作需要精确测量面另一些工作只需粗略估<
/p>
计。
Some
instruments
are
used
solely
to
determine
whether
or
not
a
circuit
is
complete.
有些仪器被使用仅仅是确定线路是否完整。
The most
common measuring and testing
instruments
are
voltage
testers,
voltmeters,
ammeters,
ohmmeters,
continuity
testers,
megohmmeters,
wattmeters
（功率计）
,
and
watt-hour
met
ers
（电度表，电表）
。
最常用的测量测试仪表有：电压测试仪，电压表，欧姆表，连续性测试仪，兆欧表，瓦特表
还有瓦特小时表。
All meters
used for measuring electrical values are basically
current meters.
所
有测量电值的表基本上都
是电流表。
They measure or compare the values
of current
flowing
through
them.
他们测量或是比较通过他们的电流值。
The
meters
are
calibrated
and the scale is
designed to read the value of the desired unit.
这些仪表可以被
校准并且设计了不同的量程，以便读出期望的数值。
1.1 SAFETY
PRECAUTION
安全预防
Correct
meter
connections
are
very
important
for
the
safety
precaution
of
the
user
and for proper
maintenance of the meters.
仪表的正确连接对于使用
者的安全预防和
仪表的正确维护是非常重要的。
A
basic
knowledge
of
the
construction
and
operation
of
meters
will
aid
the user in making proper
connections
and maintaining them in safe
working
order.
仪表的结构和操作的基本知识能帮助使用者按安全工作程序来对他们正确
连接和维护。
Many
instruments
are
designed
to
be
used
on
DC
or
AC
only,
while
others
can
be
used
interchangeably.
许多仪表被设计的只能用
于直流或只能用于交流，而其它的则可交替使
用。
Note:
It is very important to use each meter only with
the type of current for
which the meter
is designed.
注意：每种仪表只能用来测量符合设计要求的电流类型。<
/p>
Using a meter with an incorrect type of
current can result in damage to the meter
and may cause injury to the user.
如果用在不正确的电流类型中可能对仪表有危险并且
可能对使用者引起伤害
。
Some meters are
constructed to measure very low values.
许多仪表被设计成只能测量
很低的数值
Other
meters can measure extremely high values.
还有些能测量非常大的数
值。
CAUTION: Never allow a meter to exceed
its rated maximum limit.
警告：仪表不允许
超过它的额定最大值。
The
importance
of
never
allowing
the
actual
value
to
exceed
the
maximum value indicated on the meter
can not be overemphasized.
不允许被测的实际
数值超过仪表最大允许值的要求再强调也不过分。
Exceeding
maximum values can damage
the
indicating
needle,
interfere
with
proper
calibration,
and
in
some
instances
may
cause the meter to explode, resulting
in injury to the user.
超过最大值对指针有
伤害，有害于正确校准，并且在某种情况下能引起仪表爆炸造成对作用者的伤害。
Some
meters are equipped with over
correct protection. However, a current many times
greater than the
instrument
’
s design limit
may still be hazardous.
许多仪表装备
了过载保护。然而，通常情况下电流大于仪表设计的限定仍然是危险的。
2. Fundamentals of Solid-state Power
Device
固体功率器件的基本原理
In this chapter we focus on solid-state
power devices, or power semiconductors,
only
as
they
are
being
used
in
the
power
leads
or
power
circuits
to
three-phase
460
V
AC
squirrel
cage
induction
motors
for
either
phase
(voltage)
control
or
frequency
(speed) control.
本章将集中讨论固态功率
器件或功率半导体器件，并且只研究它们在采
用相控
（电压控制
）
或频率控制
（速度控制）
的三相交流
鼠笼式感应电机的功率电路中的应
用。
2.2
SOLID-STATE POWER
DEVICES
固态功率器件
The
five major types of power semiconductors used in
solid-state AC motor control
are:
有五种用于固体交流电机控制中的功率元器件：
Diodes
二极管
Thyristors[e.g., silicon-controlled
rectifiers (SCRs)]
晶闸管（例如：可控硅整流
< br>器
SCR
）
Transistors
电子晶体管
Gate-turn-off thyristors
门极可关
断晶闸管（
GTO
）
Triacs
双向可控硅
SCRs and triacs are commonly used for
phase controls.
晶闸管
SCR
和双向可控硅一般
用于相位控制（相控）
。
Various combinations of diodes, SCRs,
transistors, and GTOs
are used for
speed controls.
各种二极管，晶闸管
SCR
，电子晶体管，门极可关断晶闸
管的联合体用于频控。
The commonality of these devices is the use
of crystals of
silicon in the form of
wafers that are layered so as to form various
combinations
of
PN
junction.
这些器件的共性是：利用硅晶体形成的薄
片构成
P-N
结的各种组合。
The
P
junction is usually called
the anode and N junction is usually called the
cathode
for diodes, SCRs, and GTOs; the
corresponding terms for transistors are collector
and emitter.
对二极管，
SCR
，
GTO
一般
P
结叫正极
N
结叫负极；相
应的电子晶体管叫集
电极和发射极。
The
differences among these devices relate to how they
go into and
out of conduction and in
their available ampere and voltage capabilities. <
/p>
这些器
件的区别在于导通和关断的方法及电流和电压的容量。
Let
’
s
take
a
brief
look
at
each
of these devices in terms of these
parameters.
让我们根据他们的参数简单看一下这
些元器件。
3 Analog
Electronics
模拟电子
3.1
INTRODUCTION
介绍
3.1.1 The Contrast between Analog and
Digital
Electronics
模拟和数字电子学对照
We
have
already
explored
how
transistors
and
diodes
are
used
as
switching
devices
to process
information which is represented in digital form.
我们已经研究过三极
管和二极管怎样作为开关器件用于处理以数
字形式出现的信息。
Digital
electronics
uses
transistors
as
electrically controlled
switches: transistors
are either
saturated
or
cut
off.
数字电子学中，三极管用作电子控制开关：它不是饱
和就是截止。
The
active
region is used only in transition from
one state to he other.
（三极管的）动态区
< br>域仅用于从一种状态过渡到另一种状态。
By
contrast,
analog
electronics
depends
on
the
active
region
of
transistors
and
other types of amplifiers.
与
之相对的是，模拟电子学依赖于三极管的动态区域和其它
放大器的形式。The
Greek roots of “analog” mean “in due ratio”,
signifying in
this
usage
that
information
is
encoded
into
an
electrical
signal
which
is
proportional to the quantity being
represented.
希腊语词根“analog”的意思是“以
一定的比例”，在这里表示信息被编码成为与表达量成正比的电信号。
In
Fig.3.1
our
information
is
some
sort
of
music,
originating
physically
in
the
excitation
and resonance’s of a musical
instrument.
在图
3.1
中，我们的信息是某
种音乐，物理上由乐器的激励和共鸣产生。
The radiated sound consists in the
ordered
movement of air molecules and
is best understood ad acoustic waves.
辐
射的声波由
空气分子的有序运动组成，准确的理解为声波，
These produce motion in the diaphragm
of a microphone, which in turn produces
an electrical signal.
它使话筒的振动膜移
< br>动，依次产生电信号。
The variation in the
electrical signal are a proportional
representation
of
the
sound
waves.
电信号的变化与声波成比例。
The
electrical
signal
is amplified electronically, with an
increase in signal power occurring at the
expense of the input AC power to the
amplifier.
电信号被用电子的方法放大，即利用
输
入放大器的交流电能将信号的功率放大。
The
amplifier
output
drives
a
recording
head
and produces a wavy groove on a disk. <
/p>
放大器的输出驱动一个记录头，并且在一个圆盘
上产生起伏的沟槽
。
If
the
entire
system
is
good,
every
acoustic
variation
of
the
air
will be recorded on the
disk and, when the record is played back through a
similar
system and the signal
reradiated ad sound energy be a loudspeaker, the
resulting
sound should faithfully
reproduce the original music.
如果整个系统正常，
每一次声
波振动都会记录在圆盘上，
并且当该记录通过类似的系
统重放，
信号以声能的形式从扬声器
辐射出来，所产生的声音能
忠实地重现原始音乐。
Electronic
systems
based
on
analog
principles
form
an
important
class
of
electronic
devices.
< br>基于模拟原理的电子系统形成了一类重要的电子仪器。
Radio
and
TV
broadcasting
are
common
examples
of
analog
systems,
as
are
many
electrical
instruments used in monitoring
deflection (strain gages, for example), motion
(tachometers),
and
temperature
(thermocouples).
收音机和电视机的播放是模拟系统的
典型例子，
许多仪器也是模拟系统，
它们的应用领域包括偏差检测
（应变计量器）
运动控制
（测速仪）和温度测量（热电偶）
。
Many
electrical
instruments-voltmeters,
ohmmeters,
ammeters, and
oscilloscopes-utilize analog techniques, at least
in part.
许多电
子仪器——电压表、电流计欧姆表、
和示波器应用或至少是部分应用了模拟技术。
Analog computers existed before digital
computers were developed.
模拟计算机
< br>在数字计算机成熟之前就已存在。
In
an
analog
computer,
the
unknowns
in
a
differential
equation are modeled with electrical
signals.
在模拟计算中，用电信号模拟微分方程
的未
知量。
Such signals are integrated, scaled,
and summed electrically to yield
solutions with modes effort compared
with analytical or numerical techniques.
用
电子的方法对这些信号积分、
比例运算和求和以获得方程
的解，
比起解析或数值求解方法要
容易一些。
< br>
4.1.1 What is a Digital
Signal
什么是数字信号
A
Historical
Example.
一个历史例子“
Listen
my
children
and
you
shall
hear
of
the
midnight ride of Paul Re
vere
?”
听，我的孩子们，你们将
会听到保罗·瑞维尔午夜策
马飞奔的传奇，
to
Longfellow
’
s
poem,
Paul
Revere
was
sent
riding
through
the
New
England
countryside
by
a
signal
from
the
bell
tower
of
the
Old
North
Church
in Boston.
根据朗费罗的诗，保罗·瑞维尔通过波
士顿老北教堂的钟楼那里给新英格兰农
民发信号。
（不写：如果
英军今晚无论是从陆地还是从海上来犯，在老北教堂钟楼的拱门上
高挂一盏灯笼作为信号
）
“
One if by
land and two if by sea.
”
。
一盏灯笼表示从陆
地来，两盏灯笼表示从海上
来
。
That
is,
one
light
was
to
be
displayed
if
the
British
forces were
advancing toward Concord by the road from Boston,
and two lights
were to be displayed if
they were crossing the Mystic River to take an
indirect
route
)
那就
是说，
如果英国军队从波士顿陆地向康科德前进，展示一盏灯
，如果他们穿过
Mystic
河走间接航线，两盏灯将被展示。
The message received by the
Patriot was coded in digital form.
爱国者们
收到的消
息就是数字形式的编码。
We would say
today that the two
“
bits
”
of information were
conveyed by the code(strictly speaking,
two bits could indicate four possible
message and would require
distinguishable lights, say one red and one
white).
我
们今天将说这两个
位
的信息通过代码运传送
(
严格地说，
二位能表明
4
个可能消息，
并且
< br>要求可分辨的灯，一个红灯和一个白色的灯
)
.The
first
light
signaled
that
the
British
were advancing.
第一个灯光通知英国军队正前进，
The second
light indicated by what
route
they
were
coming.
第
2
盏灯指示他们通过什么路线来。<
/p>
Because
only
two
routes
of
advance
were envisioned, this second bit of information
could be interpreted as
indicating one
of the two routes.
因为想象只有两条路，信息的第二位能被解释
为表明
两条路线之一。
Information can be communicate in
digital form if the massage is capable of being
defined by a series of yes/no
statements.
如果信息能被一系列的
YES/NO
所定义，信
息就能以数字形式确定。
T
here
can
be
only
two
states
of
each
variable
used
in
conveying
the
information.
每
个
变
量
只<
/p>
可
能
有
两
种
状
态
在
传
送
信
息
方
面
使
用
。
Reducing
information
to
a
series
of
yes/no
statements
might
appear
to
be
a
severe
limitation
on this method,
but the method is in fact quite powerful.
< br>这种方法把信息简化为一
系列是
/
不看起来有局限性，但是这种方法实际上十分有用。
Numbers
can
be
represented
in base 2 and
the alphabet by a digital code.
数目可以以基数
2
表示，字母表可以表
示成数字代码。
Indeed,
any
situation
with
a
finite
number
of
outcomes
can
be
reduced
to
a
digital
code.
的确，有限输出的任何情形都可以被简化成数字代码。
Specifically,
n digital bits can
represent 2
∧
n states of
possible outcomes.
具体的，
n
位数字
能描述成
2
∧<
/p>
n
个可能状态。
Digital
communication
takes
a
well-defined
code
known
to
the parties at both ends, as in our
historical example.
如同在我们的历史例子中，
数字通讯能用明确定义的代码在两种情况下都通知到大家。
Analysis
of
the
Revere
Communication
Code.
瑞维尔通讯码分析。
In
order
to
fix
further
the
idea
of
digital
information,
we
shall
define
two
digital
variables
which
describe
the
Paul
Revere
communication
system,
Let
B
describe
whether
the
British
are
coming,
and L describe the
route by which they are coming, provide that they
are coming.
为了更进一步确定数字的信息的概念，
我们将定义两个来描述保罗瑞维尔通信系统的数字
变量，
<
/p>
让
B
描述是否英国人正来，
并且
L
描述他们正来的路线。
The
mathematical
variables,
B and L,
are unusual
mathematical variables
because each can
have only
two values.
数学变量，<
/p>
B
和
L
，是不平
常的数学变量，
因为每一个只能有两个值。
We
may
call
those
two
values
by
any
names
we
wish
:yes
/no,
true/false,
one/zero,
high
/low,
even <
/p>
black/white.
我们可以用我们希望的任何名字给两值
命名：
是
/
不，真
/
假，一
/
< br>0
，高
/
低，
< br>甚至黑色
/
白色。
When
this type of mathematics was used primarily for
analysis of
philosophical arguments
through symbolic logic, the values of the
variables were
called true or false,
according to the validity of the logical
propositions being
represented.
当这类数学被通过符号逻辑用于哲学论据分析时，变量的值被叫对还是错，
根据
逻辑命题被阐述的正确性。
Recently, the names one
/zero have come to be
preferred(
首选的；优先的
)
by
engineers
and
programmers
dealing
with
digital
codes.
近来，命名
1/0
已经开始被工程师和程序员
(
处理数字代码
)
更喜欢
These names
have the
obvious
advantage
of
fitting
with
the
binary
(base2)
number
system
for
representation
of
numerical
information,
but
these
names
occasionally
lend
confusion to the discussion of digital
systems.
这种命名有明显的优势，适用于二进
制数字
系统
(base2)
处理数字信息，但是这些命名偶尔对数字系
统的讨论造成混乱。
Nevertheless,
we
shall
use
1/0
of
one/zero
as
our
two
possible
states
of
the
digital
variables B and L.
虽然如此
,
我们将使用
ONE/ZERO
< br>或
1/0
作为我们数字变量
B<
/p>
和
L
的两
种可能
的状态
Thus the definitions
of B
and
L are B=1 B=0 L=1 L=0 if
the
British are
coming if the British are not coming if
coming by sea if coming by land
因此
B
和
L
的定义是如果英国人
将来，
B = 1
如果英国人不来，
B = 0
如果通过海上来，
L = 1
如
果由陆路来，
L = 0
The first light (B)uniquely determines
if he should ride.
第一个光
(B)
唯一确定他
是否骑马。
When
the first light appears, he mounts his horse.
当第一光出现时，他
骑上他的马。
But he
cannot leave until the second light (L) appears
(or fails to
appear), for the second
light reveals the route of the British and hence
defines
in part the message to be
announced.
但是他不能离开直到第
2
盏灯
(L)
出现
(
或者不出
现
) ,
对于
第
2
盏灯来说显示英国人的路线并且因此确定要被宣布的部分消
息。
Representing Digital
Information Electrically.
用电力描述数字信息。
In digital
electronics, digital variables are
represented by logic levels.
在数字电子方面，
数字变量通过逻辑级描述。
At
any
given
time,
a
voltage
is
expected
to
have
one
value
or
another, or more precisely to lie within one
region or another.
在任何规定时
间，<
/p>
电压预计有一值或者另一个，
或者更确切在一个范围内。
In
a
typical
system,
a
voltage
between 0 and 0.8 V would be considered
a digital zero, a voltage between 0.8-2 V
would be forbidden; that is if the
voltage fell within this range, you would known
that digital equipment needs repair.
在一个典型系统里，
0
和
0.8 V
之间的电压将被
认为是数字的零，在
0.8
和
2 V
之间的电压将被禁止；
如果电压属于这范围，你知道数字
设备需要修理了。
这些定义显示在图
4.1
中
< br>These definitions are shown in Fig.4.1.
As an illustration of a digital
circuit, we shall consider the amplifier-switch
as a NOT circuit.
作为一个数字电路的插
图，我们将考虑放大器开关作为一条非门电路。
The
output
of
a
NOT
circuit
is
the
digital
complement,
or
the
opposite,
of
the
input.
非电路的输出
是输入数字的
“反”
或者
“补码”
。
First
we
shall
represent
the
definition
of
the NOT circuit with a truth table.
首先我们将用一个真值表描述非电路的定义。
This is
shown in Fig.4.2: A represents the input, which
may be either 1 or 0
；
B
represent the
output
，
which may also be 1
or 0
，
but depends upon the
input.
这在
图
4.2
显示：
A
描述输入，
可
能
1
或者
0
；
B
描述输出，
也可能是
1
或者
0
，
< br>但是由输入决定。
The
NOT,
or
logical
complement,
operation
is
indicated
algebraically
by
the
equation
under the truth table.
非或者逻辑
补的操作，以真值表以下的那些方程式用代数方式被
表达。
We shall now define logic levels for
the amplifier-switch such that it performs
the NOT function.
我们现在将确定放大器开关的逻辑级这样它能执行非的功能。
The
input-output characteristic of the
circuit is repeated in Fig.403.
电路的输入输<
/p>
出特性被在图
4.3
中重复。
Clearly, we wish 10 V to be in the region for a 1 and 0.7
V to be in the region
for a 0.
显然，我们希望
10 V
< br>为
1
区域，
0.7
V
在
0
区域。
That
is
if
the
input
were
10
V
(digital
1),
the
output
should
be
less
than
0.7V
(digital
0),
and
vice
versa
（反之亦然）
.
那就是说，输入是
10
V(
数字
1)
,
输出应该少于
0.7
V(
数
字
0)
,
反之亦然。
Hence we might
consider making the region for a digital 0 to be
from 0
～
1 V, and
the region for a digital 1 to be, say, from
8
～
10 V.
因此，我们
可能考虑数字
0
的范围从
0-1V
，数字
1
的范围大约从
8
-10
V
。
This
will
work
but
leaves
insufficient range
for a working digital system.
这对一个工作的数字
系统能很好工
作，但是离开了能胜任的范围。
That
is,
it
is
desirable
to
broaden
the
range
of
values
in the
regions for 1 and 0 to allow for variations in
transistors, power supply
voltage,
noise that might get mixed in with the signal, and
the like.
那就是说，
希望扩展区域
1
和
0
的有效范围，
以允许晶体管和电源电压的变化以及混杂在信号里的噪音
等因素的影响。
In the present case, we can by trail
and error
（试凑法）
determine
that
the
region
0
～
1.5
V
as
a
digital
0
works
well
with
5
～
10
V
as
a
digital
1;
with
these
definitions the circuit operates as a NOT circuit,
that is, it performs the
logical
complement
。
These logic
levels are shown in Fig.4.4.
在目前例子中，
我们
能以错误操作的范围
0-1.5
V
作为数字
0
，好的操作范围
5 -10 V
作为数字
1
；即由于这些
定义电路作为一条并非电路，
即，它执行合乎逻辑的补足。
这些逻
辑级被用图
4.4
显示。
5 Introduction to Electrical
Machines
电机的介绍
5.1
Brief History of Electrical
Machines
电机的简要历史
Electrical machinery has been in
existence for many years.
电机存在了多年。
The
applications
of
electrical
machines
have
expanded
rapidly
since
their
first
use
many
years
ago. <
/p>
从他们多年前的第一个使用，
电机的应用已经迅速扩大了。
At
the
present
time,
applications continue
to increase at rapid rate.
目前，应用继续快速增加。
Thomas
Edison
is
given
credit
for
developing
the
concept
of
widespread
generation and
distribution of electrical power.
托马斯·爱
迪生因为电力的普遍阶
段和电力传输（配电）的概念的发展获得荣誉。
< br>He performed developmental work on
direct-current (DC) generators which
were driven by steam engines.
他对被蒸气机
驱动的直流
(DC)
发电机进行了发展的工作
。
Edison
’
s work
with electrical lights and
power
production
led
the
way
to
the
development
of
DC
motors
and
associated
control
equipment.
爱迪生对电灯和电力产品的工作带来了直流电动机和相关控制设备的发展。
Most early discoveries related to
electrical machinery operation dealt with
direct-current systems.
大多数早
期的发明都与处理直流电系统的电机操作有关。
Alternating-
current (AC) power generation and distribution
became widespread a
short time later. <
/p>
交流电
(AC)
发电机和传输后来才变得
广泛。
The primary reason for
converting to AC power production and
distribution was that transformers could be
used to increase AC voltage levels for
long-distance distribution of electrical
power.
转变为交流电能产生与传输的主要原因是变压器
能升高交流电压电平以适适合电能
的长距离传输。
Thus
the discovery of transformers allowed the
conversion of power
production and
distribution systems form DC to AC systems.
因此，变压器的发明允
许电能的产生与传输系统从
D
C
到
AC
系统的变换。
Presently,
almost
all
electrical
power
systems produce and distribute three
–
phase alternating current.
目前，几乎所有
电力系统产生与传输使用三相交流电。
Transformers
allow
the
voltage
produced
by
an
AC
generator to be increased
while decreasing the current level by a
corresponding
amount.
变压器允许交
流发电机产生的电压在以相应数量级减少电流时被增加。
This
allows
long-distance
distribution
at
a
reduced
current
level,
reduces
power
losses,
and
increases system efficiency.
这样，允许在很低的电
流下远距离传输，降低了电力
损耗，增加系统效率。
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