semiconductors.In the first category are substances which provide an easy path for an electric current. All metals are conductors, however some metals do not conduct well. Manganin, for example, is a poor conductor. Copper is a good conductor, therefore it is widely used for cables. A non-metal which conducts well is carbon. Salt water is an example of a liquid conductor.
A material which does not easily release electrons is called an insulator. Rubber, nylon, porcelain and air are all insulator. There are no perfect insulators.
An electric shock is the pathophysiological effect of an electric current through the
Its passage affects essentially the muscular, circulatory and respiratory functions and
sometimes results in serious burns. The degree of danger for the victim is a function
of the magnitude of the current, the parts of the body through which the current
passes, and the duration of current flow.
Electricity is an invisible force that is used to transfer
energy into heat, light, intelligence, or motion. Electricity
is explained in terms of electrical charge, potential differ-
ence (or voltage), electrical charge flow (or current), and
resistance to current flow. Figure 1-1 graphically illus-
trates electron flow through a conductor by comparing it
with water flow through a pipe. The normal unit of current
measurement is the ampere, whereas the normal unit of
voltage measurement is the volt. The unit of opposition to
current flow, or resistance, is the ohm...
This publication deals primarily with small and medium-sized induction motors which are the most common type of alternating current motor. The combination of new materials and more sophisticated methods for calculation, design and production have made the modern three-phase induction motor a robust and reliable prime mover.
Electrically powered road vehicles are currently more and more debated and many new prototypes of vehicles and batteries have been presented, e.g. at the 18th International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium and Exhibition in October 2001 in Berlin, Germany, the world’s largest event on this topic under the motto ‘‘Clean and efﬁcient mobility for the millennium’’.
The resistor is an electrical device whose primary function is to introduce resistance to the flow of electric
current. The magnitude of opposition to the flow of current is called the resistance of the resistor. A larger
resistance value indicates a greater opposition to current flow.
The resistance is measured in ohms. An ohm is the resistance that arises when a current of one ampere is
passed through a resistor subjected to one volt across its terminals.
Electromagnetism is fundamental to the whole of electrical and electronic engineering. It provides
the basis for understanding the uses of electricity and for the design of the whole spectrum of devices
from the largest turbo-alternators to the smallest microcircuits. This subject is a vital part of the
education of electronic engineers. Without it they are limited to understanding electronic circuits in
terms of the idealizations of circuit theory.
These power ratings and currents are given for an ambient temperature of 50°C (122°F) at the factory-set switching frequency,
used in continuous operation (factory-set switching frequency of 4 kHz for ATV71H 037M3 to D15M3X and 2.5 kHz for ATV71H D18M3X
Above this factory setting, the drive will reduce the switching frequency automatically in the event of excessive temperature rise.
For continuous operation above the factory setting, derating must be applied to the nominal drive current in accordance with the curves
on page 14.
If each voltage is connected to a circuit with the same power factor and the three currents return along the
same conductor, then the vector sum of the three return currents is zero. Thus instead of three full sized
return cables, only one of smaller size is needed. If none of the load is single phase, then the neutral is not
needed at all. High voltage supplies are nearly always three phase without a neutral conductor. There is a
great economy in distribution costs if the electricity can be supplied in three phases. ...
Automatic Voltage Regulator adjusts the excitation so that at the system design power factor, the voltage
is correct whatever the current. If however it adjusts the excitation to give the correct voltage at other
power factors, then two machines will not run in parallel. One can supply a huge leading current and the
other a huge lagging current. A “droop” is needed to give a lower voltage if the power factor lags by more
than the system design. This is achieved by the compounding. Faulty Compounding causes unstable
sharing of kVAr which can be quite violent....
More than eighty years later, it is not so much a utopian use of technical innova-
tions that marks the current trend in lifestyle advertisement, but – on a deeper
level – an aestheticisation of everyday experience that connects the commer-
cials discussed here to the avant-garde movement of the 1920s.
To accurately estimate energy savings attributable to the ENERGY STAR program, and target future efforts,
current data are needed on the extent to which each type of office equipment is turned off or successfully
enters low power mode when idle. Combined with measurements of the energy used in each power state,
we can estimate typical unit energy consumption (UEC), which, combined with number of units currently
in use, provides an estimate of total energy use, and program savings (Webber, Brown et al. 2002).
In our ongoing technical support of ...
Những nội dung chính được trình bày trong chương này gồm: Signal and Image processing, machine learning, multisim software, Kirchoff's Current Law(KCL) and Kirchoff's Voltage Law (KVL), circuit analysis. Mời các bạn cùng tham khảo.
Lecture Electric circuit theory - Basic elements of electrical circuits presents the following content: Circuit element, circuit, series circuit & parallel circuit, voltage, current, charge, flux linkage, power, energy, independent sources.
This chapter presents the following content: Sinusoidal steady-state analysis, Ohm’s law, Kirchhoff’s laws, impedance combinations, branch current method, node voltage method, mesh current method, superposition theorem, source transformation, Op Amp AC circuits.
OrCAD is a suite of tools from Cadence for the design and layout of printed circuit boards (PCBs). We are currently using version 9.2 of the OrCAD suite. This document will give you a crash course in designing an entire circuit board from start to finish. This will be a very small and simple circuit, but it will demonstrate the major concepts and introduce the tools behind completing a PCB design. After you have completed this tutorial, you will know all the steps needed to make PCBs using OrCAD. This is not, however, a guide to the inner workings of...
The long-time protection function protects cables (phases and neutral)
against overloads. This function is based on true rms measurements.
The thermal memory continuously accounts for the amount of heat in the cables,
both before and after tripping, whatever the value of the current (presence of
an overload or not). The thermal memory optimises the long-time protection
function of the circuit breaker by taking into account the temperature rise in the
cables. The thermal memory assumes a cable cooling time of approximately
Many recent texts place instructors in the difficult position of chosing between authoritative, state-of-the art coverage and an approach that is highly supportive of student learning. This carefully developed text was widely praised by reviewers for both its great clarity and its rigor. The book balances theory and practice in depth without getting bogged down in excessive technical or mathematical language and has abundant coverage of current topics of interest, such as programmable devices, computer-aided design, and testability.