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Crowbar (circuit)
A crowbar circuit is an electrical circuit used for preventing an overvoltage or surge condition of an AC power supply unit from damaging the circuits attached to the power supply. It operates by putting a short circuit or low resistance path across the voltage output (Vo), like dropping a Crowbar (tool), crowbar across the output terminals of the power supply. Crowbar circuits are frequently implemented using a thyristor, TRIAC, trisil or thyratron as the shorting device. Once triggered, they depend on the current (electricity), current-limiting circuitry of the power supply or, if that fails, the blowing of the line fuse (electrical), fuse or tripping the circuit breaker. The name is derived from having the same effect as throwing a crowbar over exposed power supply terminals to short the output. Example In the following example crowbar circuit, the LM431 adjustable Zener_diode, zener regulator controls the gate of the TRIAC. The Voltage_divider, resistor divider of R1 and R2 p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Circuit
An electrical network is an interconnection of electrical components (e.g., battery (electricity), batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage sources, current sources, Electrical resistance and conductance, resistances, inductances, capacitances). An electrical circuit is a network consisting of a closed loop, giving a return path for the current. Thus all circuits are networks, but not all networks are circuits (although networks without a closed loop are often referred to as "open circuits"). A resistive network is a network containing only resistors and ideal current and voltage sources. Network analysis (electrical circuits), Analysis of resistive networks is less complicated than analysis of networks containing capacitors and inductors. If the sources are constant (Direct current, DC) sources, the result is a DC network. The effective resistance and current dist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clamp (circuit)
A clamper (or clamping circuit or clamp) is an electronic circuit that fixes either the positive or the negative peak excursions of a signal to a defined voltage by adding a variable positive or negative DC voltage to it. The clamper does not restrict the peak-to-peak excursion of the signal (clipping); it moves the whole signal up or down so as to place its peaks at the reference level. A diode clamp (a simple, common type) consists of a diode, which conducts electric current in only one direction and prevents the signal exceeding the reference value; and a capacitor, which provides a DC offset from the stored charge. The capacitor forms a time constant with a resistor load, which determines the range of frequencies over which the clamper will be effective. General function A clamper will bind the upper or lower extreme of a waveform to a fixed DC voltage level. These circuits are also known as DC voltage restorers. Clampers can be constructed in both positive and negative po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Voltage Restoration
Dynamic voltage restoration (DVR) is a method of overcoming voltage sags and swells that occur in electrical power distribution. These are a problem because spikes consume power and sags reduce efficiency of some devices. DVR saves energy through voltage injections that can affect the phase and wave-shape of the power being supplied. Devices used for DVR include static var devices, which are series compensation devices that use voltage source converters (VSC). The first such system in North America was installed in 1996 - a 12.47 kV system located in Anderson, South Carolina. Operation The basic principle of dynamic voltage restoration is to inject a voltage of the magnitude and frequency necessary to restore the load side voltage to the desired amplitude and waveform, even when the source voltage is unbalanced or distorted. Generally, devices for dynamic voltage restoration employ gate turn off thyristors, (GTO) solid state power electronic switches in a pulse-width mod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microswitch
Comparison of some different switches A miniature snap-action switch, also trademarked and frequently known as a micro switch or microswitch, is an electric switch that is actuated by very little physical force, through the use of a tipping-point mechanism, sometimes called an "over-center" mechanism. The defining feature of micro switches is that a relatively small movement at the actuator button produces a relatively large movement at the electrical contacts, which occurs at high speed (regardless of the speed of actuation). Switching happens reliably at specific and repeatable positions of the actuator, which is not necessarily true of other mechanisms. Most successful designs also exhibit hysteresis, meaning that a small reversal of the actuator is insufficient to reverse the contacts; there must be a significant movement in the opposite direction. Both of these characteristics help to achieve a clean and reliable interruption to the switched circuit. They are very common d ... [...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] |
Inductive Output Tube
The inductive output tube (IOT) or klystrode is a variety of linear-beam vacuum tube, similar to a klystron, used as a power amplifier for high frequency radio waves. It evolved in the 1980s to meet increasing efficiency requirements for high-power RF amplifiers in radio transmitters. The primary commercial use of IOTs is in UHF television transmitters, where they have mostly replaced klystrons because of their higher efficiencies (35% to 40%) and smaller size. IOTs are also used in particle accelerators. They are capable of producing power output up to about 30 kW continuous and 7 MW pulsed and power gains of 20–23 dB at frequencies up to about a gigahertz. History The inductive output tube (IOT) was invented in 1938 by Andrew V. Haeff. A patent was later issued for the IOT to Andrew V. Haeff and assigned to the Radio Corporation of America (RCA). During the 1939 New York World's Fair the IOT was used in the transmission of the first television images from the E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Klystron
A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian,Pond, Norman H. "The Tube Guys". Russ Cochran, 2008 p.31-40 which is used as an amplifier for high radio frequencies, from ultra high frequency, UHF up into the microwave range. Low-power klystrons are used as oscillators in terrestrial microwave relay communications links, while high-power klystrons are used as output tubes in UHF television transmitters, satellite communication, radar transmitters, and to generate the drive power for modern particle accelerators. In a klystron, an electron beam interacts with radio waves as it passes through cavity resonator, resonant cavities, metal boxes along the length of a tube. The electron beam first passes through a cavity to which the input signal is applied. The energy of the electron beam amplifies the signal, and the amplified signal is taken from a cavity at the other end of the tube. The output signal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CMOS
Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss ", , ) is a type of MOSFET, metal–oxide–semiconductor field-effect transistor (MOSFET) semiconductor device fabrication, fabrication process that uses complementary and symmetrical pairs of p-type semiconductor, p-type and n-type semiconductor, n-type MOSFETs for logic functions. CMOS technology is used for constructing integrated circuit (IC) chips, including microprocessors, microcontrollers, memory chips (including Nonvolatile BIOS memory, CMOS BIOS), and other digital logic circuits. CMOS technology is also used for analog circuits such as image sensors (CMOS sensors), data conversion, data converters, RF circuits (RF CMOS), and highly integrated transceivers for many types of communication. In 1948, Bardeen and Brattain patented an insulated-gate transistor (IGFET) with an inversion layer. Bardeen's concept forms the basis of CMOS technology today. The CMOS process was presented by Fairchild Semico ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault Current
In an electric power system, a fault is a defect that results in abnormality of electric current. A fault current is any abnormal electric current. For example, a short circuit in which a live wire touches a neutral or ground wire is a fault. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire (phase or neutral) or a blown fuse or circuit breaker. In a "ground fault" or "earth fault", current flows into the earth. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a polyphase system, a fault may affect all phases equally, which is a "symmetric fault". If only some phases are affected, the resulting "asymmetric fault" becomes more complicated to analyse. The analysis of these types of faults is often simplified by using methods such as symmetrical components. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage Dip
A voltage sag (U.S. English) or voltage dip (British English) is a short-duration reduction in the voltage of an electric power distribution system. It can be caused by high current demand such as inrush current (starting of electric motors, transformers, heaters, power supplies) or fault current ( overload or short circuit) elsewhere on the system. Voltage sags are defined by their magnitude or depth, and duration. A voltage sag happens when the RMS voltage decreases between 10 and 90 percent of nominal voltage for one-half cycle to one minute. Some references define the duration of a sag for a period of 0.5 cycle to a few seconds, and a longer duration of low voltage would be called a ''sustained sag''. The definition of voltage sag can be found in IEEE 1159, 3.1.73 as "A variation of the RMS value of the voltage from nominal voltage for a time greater than 0.5 cycles of the power frequency but less than or equal to 1 minute. Usually further described using a modifier indicating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low Voltage Ride Through
In electrical power engineering, fault ride through (FRT), sometimes under-voltage ride through (UVRT), or low voltage ride through (LVRT), is the capability of electric generators to stay connected in short periods of lower electric network voltage (cf. voltage sag). It is needed at distribution level ( wind parks, PV systems, distributed cogeneration, etc.) to prevent a short circuit at HV or EHV level from causing a widespread loss of generation. General concept Many generator designs use electric current flowing through windings to produce the magnetic field on which the motor or generator operates. This is in contrast to designs that use permanent magnets to generate this field instead. Such devices may have a minimum working voltage, below which the device does not work correctly, or does so at greatly reduced efficiency. Some will disconnect themselves from the circuit when these conditions apply. The effect is more pronounced in doubly-fed induction generators (DFIG), w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Network
An electric power system is a network of electrical components deployed to supply, transfer, and use electric power. An example of a power system is the electrical grid that provides power to homes and industries within an extended area. The electrical grid can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centers to the load centers, and the distribution system that feeds the power to nearby homes and industries. Smaller power systems are also found in industry, hospitals, commercial buildings, and homes. A single line diagram helps to represent this whole system. The majority of these systems rely upon three-phase AC power—the standard for large-scale power transmission and distribution across the modern world. Specialized power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners, submarines, and automobiles. History In 18 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
