The Navy Electricity and Electronics Training Series (NEETS) was developed for use by personnel in many electrical- and electronic-related Navy ratings. Written by, and with the advice of, senior technicians in these ratings, this series provides beginners with fundamental electrical and electronic concepts through self-study. The presentation of this series is not oriented to any specific rating structure, but is divided into modules containing related information organized into traditional paths of instruction. The series is designed to give small amounts of information that can be easily digested before advancing further into the more complex material. For a student just becoming acquainted with electricity or electronics, it is highly recommended that the modules be studied in their suggested sequence. While there is a listing of NEETS by module title, the following brief descriptions give a quick overview of how the individual modules flow together.
A magnetic compass doesn’t make a very convenient meter. It has to be lying flat, and the coil has to be aligned with the compass needle when there is no current. But of course, electrical and elec- tronic devices aren’t all oriented so as to be aligned with the north geomagnetic pole! But the exter- nal magnetic field doesn’t have to come from the earth. It can be provided by a permanent magnet near or inside the meter. This supplies a stronger magnetic force than does the earth’s magnetic field, and therefore makes it possible to make a meter that can detect much weaker currents. Such a meter can be turned in any direction, and its operation is not affected. The coil can be attached directly to the meter pointer, and suspended by means of a spring in the field of the magnet. This type of me- tering scheme, called the D’Arsonval movement, has been around since the earliest days of electricity, but it is still used in some metering devices today. The assembly is shown in Fig. 3-4. This is the basic principle of the ammeter.
A static synchronous compensator (STATCOM), also known as a static synchronous condenser (STATCON), is a regulating device used on alternating current electricity transmission networks. It is based on a power electronics voltage-source converter and can act as either a source or sink of reactive AC power to an electricity network. If connected to a source of power it can also provide active AC power. It is a member of the FACTS family of devices. A static VAR compensator can also be used for voltage stability. However, a STATCOM has better characteristics than an SVC. When the system voltage drops sufficiently to force the STATCOM output current to its ceiling, its maximum reactive output current will not be affected by the voltage magnitude. Therefore, it exhibits constant current characteristics when the voltage is low under the limit. In addition, the speed of response of a STATCOM is faster than that of an SVC and the harmonic emission is lower.
Agarwal and Lang have been working together for the past eight years on a fresh approach to teaching circuits. For several decades, MIT had offered a traditional course in circuits designed as the first core undergraduate course in EE. But by the mid-‘90s, vast advances in semiconductor technology, coupled with dramatic changes in students’ backgrounds evolving from a ham radio to computer culture, had rendered this traditional course poorly motivated, and many parts of it were virtually obsolete. Agarwal and Lang decided to revamp and broaden this first course for EE, ECE or EECS by establishing a strong connection between the contemporary worlds of digital and analog systems, and by unifying the treatment of circuits and basic MOS electronics. As they developed the course, they solicited comments and received guidance from a large number of colleagues from MIT and other universities, students, and alumni, as well as industry leaders.
The electrical solution turned out to be more cost effective. Early digital electronics systems were based on magnetically controlled switches (or relays). They were mainly used in the implementation of very simple logic networks. Examples of such are train safety systems, where they are still being used at present. The age of digital electronic computing only started in full with the introduction of the vacuum tube. While originally used almost exclusively for analog processing, it was realized early on that the vacuum tube was useful for digital computations as well. Soon complete computers were realized. The era of the vacuum tube based computer culminated in the design of machines such as the ENIAC (intended for computing artillery firing tables) and the UNIVAC I (the first successful commercial computer). To get an idea about integration density, the ENIAC was 80 feet long, 8.5 feet high and several feet wide and incorporated 18,000 vacuum tubes. It became rapidly clear, however, that this design technology had reached its limits. Reliability problems and excessive power consumption made the implementation of larger engines economically and practically infeasible.
Now that a complete circuit has been introduced and examined in detail, we can begin the application of computer methods. As men- tioned in Chapter 1, three software packages will be introduced to demonstrate the options available with each and the differences that exist. All have a broad range of support in the educational and industrial communities. The student version of PSpice (OrCAD Release 9.2 from Cadence Design Systems) will receive the most attention, followed by Electronics Workbench from Multisim and then a few sample programs using a programming language called C . Each approach has its own characteristics with procedures that must be followed exactly; other- wise, error messages will appear. Do not assume that you can “force” the system to respond the way you would prefer—every step is well defined, and one error on the input side can result in results of a mean- ingless nature. At times you may believe that the system is in error because you are absolutely sure you followed every step correctly. In such cases, accept the fact that something was entered incorrectly, and review all your work very carefully. All it takes is a comma instead of a period or a decimal point to generate incorrect results.
Before the 1960s, semiconductor engineering was regarded as part of low-current and low-voltage electronic engineering. The currents used in solid-state devices were below one ampere and voltages only a few tens of volts. The year 1970 began one of the most exciting decades in the history of low-current electronics. A number of companies entered the field, including Analog Devices, Computer Labs, and National Semiconductor. The 1980s represented high growth years for integrated circuits, hybrid, and modular data converters. The 1990s major applications were industrial process control, measurement, instrumentation, medicine, audio, video, and computers. In addition, communications became an even bigger driving force for low-cost, low-power, high-performance converters in modems, cell-phone handsets, wireless infrastructure, and other portable applications. The trends of more highly integrated functions and power dissipation drop have continued into the 2000s.
Instant Answer A caution sticker (you'll know it--it says "Caution") on an electric or electronic device in a PC alerts you to possible equipment damage. A warning label (says "Warning" and has lightning bolts, a skull and crossbones, or the like) alerts you to possible electrocution, which could hurt you. Shocking Information Just to quench your curiosity, inside the power supply, one part in particular should keep you out: a 1,000-microfarad capacitor. Capacitors store electricity, even when the power is off. This particular capacitor performs line conditioning by absorbing any power coming in above the normal level and using it to replace power below normal levels. If you were to touch the capacitor, it would shock you--potentially with bodily harm or worse. Because you can buy a new power supply in the range of $25 to $80, I'm not sure it's worth risking your life to open up the power supply to try to fix it. A good quality power supply should last for years, providing the computer with stable electrical current, assuming that it has been protected adequately. On the other hand, a low quality, faulty, or overloaded power supply can cause all kinds of problems in a system. A bad power supply can cause hard disk drives to develop bad sectors and affect memory to cause what seem like software bugs-- problems that are usually hard to pin on the power supply.
Note in Table 1.1 the extreme range between the conductor and insulating mate- rials for the 1-cm length (1-cm 2 area) of the material. Eighteen places separate the placement of the decimal point for one number from the other. Ge and Si have re- ceived the attention they have for a number of reasons. One very important consid- eration is the fact that they can be manufactured to a very high purity level. In fact, recent advances have reduced impurity levels in the pure material to 1 part in 10 bil- lion (1 10,000,000,000). One might ask if these low impurity levels are really nec- essary. They certainly are if you consider that the addition of one part impurity (of the proper type) per million in a wafer of silicon material can change that material from a relatively poor conductor to a good conductor of electricity. We are obviously dealing with a whole new spectrum of comparison levels when we deal with the semi- conductor medium. The ability to change the characteristics of the material signifi- cantly through this process, known as “doping,” is yet another reason why Ge and Si have received such wide attention. Further reasons include the fact that their charac- teristics can be altered significantly through the application of heat or light—an im- portant consideration in the development of heat- and light-sensitive devices.
There you have it—the world of electricity reduced to everyday items. Since these components are so similar, all the math tricks you might have learned apply as well to one system as they do to the other. Remember Fourier’s theo- rems? They were discovered for mechanical systems long before anyone real- ized that they work for electrical circuits as well. Remember all that higher math you used to know or are just now learning about—Laplace transforms, integrals, derivatives, etc.? It all works the same in both worlds. You can solve a mechanical system using Laplace methods just the same as an electrical circuit. Back in the 1950s and 1960s, the government spent mounds of dough using elec- trical circuits to model physical systems as described before. Why? You can get into all sorts of integrals, derivatives, and other ugly math when modeling real- world systems. All that can get jumbled quickly after a couple of orders of com- plexity. Think about an artillery shell ﬁ red from a tank. How do you predict where it will land? You have the friction of the air, the mass of the shell, the spring of the recoil. Instead of trying to calculate all that math by hand, you can build a cir- cuit with all the various electrical components representing the mechanical ones, hook up an oscilloscope, and ﬁ re away. If you want to test 1000 different weights of artillery at different altitudes, electrons are much cheaper than gunpowder. 4
The primary aim of the material in this text is to provide the fundamental analytical and underpin- ning knowledge and techniques needed to success- fully complete scientific and engineering principles modules of Degree, Foundation Degree and Higher National Engineering programmes. The material has been designed to enable students to use techniques learned for the analysis, modelling and solution of realistic engineering problems at Degree and Higher National level. It also aims to provide some of the more advanced knowledge required for those wishing to pursue careers in mechanical engineer- ing, aeronautical engineering, electronics, commu- nications engineering, systems engineering and all variants of control engineering.