|
Electrical Efficiency
The efficiency of a system in electronics and electrical engineering is defined as useful power output divided by the total electrical power consumed (a vulgar fraction, fractional Expression (mathematics), expression), typically denoted by the Greek alphabet, Greek small letter eta (η – ήτα). : \mathrm=\frac If energy output and input are expressed in the same units, efficiency is a dimensionless number. Where it is not customary or convenient to represent input and output energy in the same units, efficiency-like quantities have units associated with them. For example, the heat rate (efficiency), heat rate of a fossil fuel power station, fossil fuel power plant may be expressed in British thermal unit, BTU per kilowatt-hour. Luminous efficacy of a light source expresses the amount of visible light for a certain amount of power transfer and has the units of lumen (unit), lumens per watt. Efficiency of typical electrical devices ''Efficiency'' should not be confused ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronics
Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield of physics and electrical engineering which uses Passivity (engineering), active devices such as transistors, diodes, and integrated circuits to control and amplify the flow of electric current and to convert it from one form to another, such as from alternating current (AC) to direct current (DC) or from analog signal, analog signals to digital signal, digital signals. Electronic devices have significantly influenced the development of many aspects of modern society, such as telecommunications, entertainment, education, health care, industry, and security. The main driving force behind the advancement of electronics is the semiconductor industry, which continually produces ever-more sophisticated electronic devices and circuits in respo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Premium Efficiency
Premium efficiency, when used in reference to specific types of Electric Motors (with a rotating shaft), is a class of motor efficiency. As part of a concerted effort worldwide to reduce energy consumption, CO2 emissions and the impact of industrial operations on the environment, various regulatory authorities in many countries have introduced, or are planning, legislation to encourage the manufacture and use of higher efficiency electrically powered motors. This article looks at the development of the premium efficiency standard (IE3) and premium efficiency motors (PEMs) and associated environmental, legal and energy-related topics. History The oil crisis and the worldwide need for more power, more electrical power, and consequently more power stations have raised energy conservation awareness. In 1992 the U.S. Congress, as part of the Energy Policy Act (EPAct) set minimum efficiency levels (see Table B-1) for electric motors. In 1998 the European Committee of Manufacture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna Efficiency
Antenna ''apertureillumination efficiency is a measure of the extent to which an antenna or array is uniformly excited or illuminated. It is typical for an antenna pertureor array to be intentionally under-illuminated or under-excited in order to mitigate sidelobes and reduce antenna temperature. It is not to be confused with radiation efficiency or antenna efficiency. Definition Antenna pertureillumination efficiency is defined as "The ratio, usually expressed in percent, of the maximum directivity of an antenna pertureto its standard directivity." It is synonymous with normalized directivity. Standard eferencedirectivity is defined as "The maximum directivity from a planar aperture of area A, or from a line source of length L, when excited with a uniform-amplitude, equiphase distribution." Key to understanding these definitions is that "maximum" directivity refers to the direction of maximum radiation intensity, i.e., the main lobe. Therefore, illumination efficie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signals
A signal is both the process and the result of Signal transmission, transmission of data over some transmission media, media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology. In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' includes audio signal, audio, video, speech, image, sonar, and radar as examples of signals. A signal may also be defined as observable change in a quantity over space or time (a time series), even if it does not carry information. In nature, signals can be actions done by an organism to alert other organisms, ranging from the release of plant chemicals to warn nearby plants of a predator, to sounds or motions made by animals to alert other animals of food. Signa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impedance Bridging
In audio engineering and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance. The load measures the source's voltage while minimally drawing current or affecting it. Explanation When the output of a device (consisting of the voltage source ''V''S and output impedance ''Z''S in illustration) is connected to the input of another device (the load impedance ''Z''L in the illustration), these two impedances form a voltage divider: : V_L = \frac V_S \, . One can maximize the signal level ''V''L by using a voltage source whose output impedance ''Z''S is as small as possible and by using a receiving device whose input impedance ''Z''L is as large as possible. When Z_L \gg Z_S (typically by at least ten times), this is called a ''bridging connection'' and has a number of effects including: * Advantages: ** Reduces the 6dB attenuation incurred by impedance matc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating Temperature
An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the maximum operating temperature (or peak operating temperature). Outside this range of safe operating temperatures the device may fail. It is one component of reliability engineering. Similarly, biological systems have a viable temperature range, which might be referred to as an "operating temperature". Ranges Most semiconductor devices are manufactured in several temperature grades. Broadly accepted grades are: *Commercial: 0 °C to 70 °C () *Industrial: −40 °C to 85 °C () *Military: −55 °C to 125 °C () Nevertheless, each manufacturer defines its own temperature grades so designers must pay attention to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Supply
A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, electric current, current, and frequency to power the load. As a result, power supplies are sometimes referred to as electric power converters. Some power supplies are separate standalone pieces of equipment, while others are built into the load appliances that they power. Examples of the latter include power supplies found in desktop computers and consumer electronics devices. Other functions that power supplies may perform include limiting the current drawn by the load to safe levels, shutting off the current in the event of an electrical fault, power conditioning to prevent electronic noise or voltage surges on the input from reaching the load, power-factor correction, and storing energy so it can continue to power the load in the event of a temporary interruption in the source power ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Battery (electricity)
An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons. When a battery is connected to an external electric load, those negatively charged electrons flow through the circuit and reach the positive terminal, thus causing a redox reaction by attracting positively charged ions, or cations. Thus, higher energy reactants are converted to lower energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term "battery" specifically referred to a device composed of multiple cells; however, the usage has evolved to include devices composed of a single cell. Primary (single-use or "disposable") batteries are used once and discarded, as the electrode mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System
A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, structure and purpose and is expressed in its functioning. Systems are the subjects of study of systems theory and other systems sciences. Systems have several common properties and characteristics, including structure, function(s), behavior and interconnectivity. Etymology The term ''system'' comes from the Latin word ''systēma'', in turn from Greek language, Greek ''systēma'': "whole concept made of several parts or members, system", literary "composition"."σύστημα" , Henry George Liddell, Robert Scott, ''A Greek–English Lexicon'', on Pers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thévenin's Theorem
As originally stated in terms of direct-current resistance (electricity), resistive circuits only, Thévenin's theorem states that ''"Any linear circuit, linear electrical network containing only voltage source, voltage sources, current source, current sources and resistance (electricity), resistances can be replaced at terminals by an equivalent combination of a voltage source in a series and parallel circuit, series connection with a resistance ."'' * The equivalent voltage is the voltage obtained at terminals of the network with terminals open-circuit voltage, open circuited. * The equivalent resistance is the resistance that the circuit between terminals and would have if all ideal voltage sources in the circuit were replaced by a short circuit and all ideal current sources were replaced by an open circuit (i.e., the sources are set to provide zero voltages and currents). * If terminals and are connected to one another (short), then the current flowing from and wil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maximum Power Theorem
In electrical engineering, the maximum power transfer theorem states that, to obtain ''maximum'' external power from a power source with internal resistance, the resistance of the load must equal the resistance of the source as viewed from its output terminals. Moritz von Jacobi published the maximum power (transfer) theorem around 1840; it is also referred to as "Jacobi's law". The theorem results in maximum ''power'' transfer from the power source to the load, but not maximum ''efficiency'' of useful power out of total power consumed. If the load resistance is made larger than the source resistance, then efficiency increases (since a higher percentage of the source power is transferred to the load), but the ''magnitude'' of the load power decreases (since the total circuit resistance increases). If the load resistance is made smaller than the source resistance, then efficiency decreases (since most of the power ends up being dissipated in the source). Although the total power ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
