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Topic: Maximum prospective short circuit current

	Circuit breaker Information - cutler hammer circuit breaker
		Circuit surplus circuit breaker breakers are often implemented with a solenoid (electromagnet) whose strength increases as the current increases and eventually trips the circuit breaker.
		Circuit ge circuit breaker breakers for larger currents are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism.
		Current wiring a gfi circuit breaker interruption in a high-voltage circuit-breaker is obtained by separating two contacts in a medium, such as sulfur hexafluoride (SF), having excellent dielectrical and arc quenching properties.
	www.inanot.com /Ina-Electronics_Topics_C_-_Cm-/Circuit_breaker.html (3041 words)

	Circuit breaker Summary
		Circuit breakers are made in varying sizes, from small devices which protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.
		Circuit breakers for larger currents are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism.
		Current interruption in a high-voltage circuit-breaker is obtained by separating two contacts in a medium, such as sulfur hexafluoride (SF), having excellent dielectrical and arc quenching properties.
	www.bookrags.com /Circuit_breaker (3363 words)

	Why opt for Circuit breaker? (Site not responding. Last check: 2007-09-10)
		Basically, Circuit breakers are often operated with a solenoid (electromagnet) whose strength increases as the current increases and accordingly, trips the circuit breaker.
		Circuit breakers for larger currents are usually arranged with pilot devices to detect a fault current and to operate the trip opening mechanism.
		The maximum short-circuit current that a breaker can withstand is decided by testing; moreover, it is necessary to note that application of a breaker in a circuit with a higher prospective short-circuit current may lead in disruption of circuit breaker to safely interrupt a fault.
	articles.jimtrade.com /articles_topics.asp?Topic=202 (827 words)

	March-April 2002: Circuit Overcurrent Protection
		At current zero, the power input is removed, the contact-polarity is reversed, and there is a race between the factors that tend to cool the arc plasma and the factors such as the circuit voltage that tend to cause arc reignition.
		Circuit breakers are designed to interrupt short-circuit fault currents ranging from 10 kA in residential branch circuits through 200 kA in industrial and commercial circuits, and much of this design involves control of the associated high current arc within the circuit breaker, with arc extinction and circuit interruption at current zero.
		Residential circuit breakers are qualified to UL 4893 and are a general category4 that includes single and two-pole circuit breakers with continuous currents of 225 A or less, and with voltage ratings of 120 V, 127 V, 120/240 V. These breakers may also be used in industrial/commercial applications.
	www.iaei.org /subscriber/magazine/02_b/kimblin.htm (3989 words)

	The Guide - MEM Technical Support
		Whether fuses or circuit breakers are utilised in a distribution system it is necessary to ensure that all the requirements of the 16th Edition of the IEE Wiring Regulations are complied with.
		These are current limiting type moulded case circuit breakers and as such it is not possible to assess short circuit discrimination by overlapping time current curves.
		In response to a short circuit fault the operation of the upstream circuit breaker creates an impedance which in conjunction with the impedance of the downstream device enables the downstream device to handle the short circuit potentially possible at this point of application.
	www.memonline.com /cb2.html (1423 words)

	: : PECO INDUSTRIES : : GLOSSARY :>>>
		Short Circuit Protector Device - A device intended to protect a circuit or parts of a circuit against short circuit currents by interrupting them.
		The continuous current rating of the Fuse Link should not be less than the full load current of the circuit.
		A device that by the fusing of one or more of its specially designed and proportioned components opens the circuit in which it is inserted by breaking the current when this exceeds a given value for a sufficient time.
	www.pecoindustries.com /glossary.html (1169 words)

	Circuit breaker with improved arc interruption function - Patent 6128168
		A fault current interrupter is provided by the parallel combination of a polymer current limiter and a voltage dependent resistor connected across a pair of separable contacts to permit the interruption of current without the occurrence of arcing between the contacts when the contacts first become separated.
		The polymer current limiter is selected to have a relatively low resistance at quiescent operating currents and a substantially higher resistance at short circuit overcurrents.
		The current through the power bus is sensed by means of a current transformer arranged with its primary winding comprising the power bus and with its secondary winding connected with an operating mechanism to rapidly open the contact assembly 15 when the current reaches a predetermined value.
	www.freepatentsonline.com /6128168.html (5760 words)

	The New GR-1089-CORE
		In such cases, the current limiter is bypassed, and the limiter maximum operating threshold current is applied to the port.
		For first-level testing, the current is set to the maximum current that would not be interrupted by the current limiter within a 15-minute period.
		This test current is the maximum current that would not be interrupted or reduced by the specified current limiter within the test duration (5 or 900 seconds).
	www.ce-mag.com /archive/03/ARG/maytum2.html (2210 words)

	Bloomberg.com: Financial Glossary
		The maximum number of shares of stock of a company allowed in the articles of incorporation, which may be changed only by a shareholder vote.
		As a result, the short interest is often an indicator of the amount of pessimism in the market about a particular security, although there are other reasons to short that are not related to pessimism.
		The theory that a large interest in short positions in stocks will precede a rise in the market prices, because the short positions must eventually be covered by purchases of the stock.
	www.bloomberg.com /analysis/glossary/bfgloss.htm (6384 words)

	Ship Electrical Standards (2002) \| TP 127 \| Marine Safety (Site not responding. Last check: 2007-09-10)
		a circuit breaker with an instantaneous trip setting of not more than 90% of the breaking capacity of the device protected and the back-up protective device shall have a breaking capacity not less than the prospective short-circuit current at the point where it is installed and the time-current characteristics shall be suitably co-ordinated.
		8.5 The maximum asymmetrical rms short-circuit current shall be assumed to be equal to the sum of the generator contribution based on circuit impedances including direct axis sub-transient reactances of generators, and the motor contribution based on 4 times the rated current of motors.
		K2 Ratio of the maximum rms asymmetrical current in one phase at one-half cycle to the rms value of the symmetrical current.
	www.tc.gc.ca /marinesafety/TP/Tp127/system.htm (481 words)

	Electric power engineering - IEC Short circuit ratings for the Circuit Breakers
		The making current Icm must be biger than the peak value ip of shc current and specifies the maximum curent which the CB withstand to in respect to the electro-dynamic forces produced by the inrush current of shc.
		Icu capacity indicates the maximum theoretical fault level of the CB and this has to be matched (equal or higher) with the calculated prospective fault (symmetrical) value of the installation at the point of connection (i.e.
		As you described, during a short circuit you have two phenomenoms: A 'mechanical force' that is caused by the current and that is directly proportional to the value of the current and a thermal loss (I^2t), that is depending on the value of the current* and on the duration time of the short circuit.
	www.eng-tips.com /viewthread.cfm?qid=81200 (3124 words)

	Short circuit - Wikipedia, the free encyclopedia
		Tree limbs cause a short circuit during a storm
		In electrical devices, unintentional short circuits are usually caused when a wire's insulation breaks down, or when another conducting material is introduced, allowing charge to flow along a different path than the one intended.
		The magnitude of current varies in all the phases during an asymmetrical short circuit.
	en.wikipedia.org /wiki/Short_circuit (959 words)

	Electrical Fires!— Why not avoid them?
		The maximum fault current that would have been available within a typical building about 25 years ago was in the range of 3KA to 5KA, depending on the proximity of the building to the substation.
		Miniature Circuit Breakers or MCB`s are switches with the feature of automatic switching off in the event of an overcurrent either by its magnetic element (which operates in a short time on large fault currents) or by its thermal element (which operates with a graded time delay related to the intensity of the current).
		Residual current circuit breaker (also called ‘Earth leakage circuit breaker’) monitors a circuit from this aspect of balance in the current flow in the two paths and isolates the circuit in the event of an unbalance exceeding the set limit of 30mA.
	members.tripod.com /~bhavani/ELE_FIRE.HTM (3913 words)

	Maximum prospective short circuit current - Wikipedia, the free encyclopedia
		The short circuit current should be of the order of around 200 A or higher for normal 10 A or 16 A outlet to guarantee that the normal wire protecting fuse or breaker will quickly disconnect the supply in case of short circuit.
		Quick disconnecting is needed, because in live-ground short circuit the grounding pin potential on the power outlet can rise compared to the local earth (concrete floor, water pipe etc.) during short circuit to a dangerous voltage, which needs to be shut down quickly for safety.
		If the short circuit current is lower than this figure, special precautions needs to be taken to make sure that the system is safe; those usually include using a residual current device for extra protection.
	en.wikipedia.org /wiki/Maximum_prospective_short_circuit_current (483 words)

	Electrical Short Circuit (Site not responding. Last check: 2007-09-10)
		Maximum prospective short circuit current - The maximum prospective short circuit current is the maximum electrical current which can flow in a particular electrical system under short circuit conditions.
		Short circuit - A short circuit (sometimes abbreviated to short or s/c) is an accidental low-resistance connection between two nodes of an electrical circuit that are meant to be at different voltages.
		This can be caused by short circuit, by incorrect installation, or by misuse such as running a high-powered appliance off a low-power extension cable.
	ho13.georgeandbills.com /electricalshortcircuit.html (588 words)

	March-April 2002: Overcurrent Protection and the NEC
		This requirement excludes the use of 300-V fuses in 3-phase, 4-wire circuits rated 480Y/277 V. Since the voltage from linetoneutral is 277 V in those circuits, it might seem appropriate to use 300-V fuses.
		However, a circuit breaker rated 480Y/277V would be suitable for use on a 240-V ungrounded or impedance grounded system since the line-to-line voltage is lower than the lower number in the slash rating.
		It consists of a maximum current and the voltage at which the device is rated to interrupt the circuit.
	www.iaei.org /subscriber/magazine/02_b/manche.htm (2309 words)

	[No title]
		The difference is the volt drop in the loop due to the current, and loop impedance is calculated from voltage difference divided by current.
		Since the loop current is very high, its duration must be short and must be limited to two cycles (or four half-cycles) or 40 ms for a 50 Hz supply.
		The current is usually switched by a thyristor or a triac, the firing time being controlled by an electronic timing circuit It is very important to have already checked the continuity of the protective system before carrying out this test.
	www.tlc-direct.co.uk /Book/8.6.2.htm (986 words)

	Pro Fuse International - Fuse User - FAQ
		The prospective short circuit current is the value of the current that would flow if there was no protection in the circuit.
		For instance, without a fuselink an asymmetrical short circuit current of 10,000 A at 230V a.c.could pass through the circuit during several cycles.
		For a prospective short-circuit current of 10,000 Amp r.m.s.
	www.profuseinternational.com /faq/shortcircuits.html (316 words)

	: : PECO INDUSTRIES : : FAQS : >>>
		For the prospective short circuit current of 10,000 Amp rms with a totally asymmetrical current, the maximum value could reach 25,000 Amp peak.
		If a protective device cuts off a short circuit current in less than one half cycle, before it reaches its total available (and highly destructive) peak value, the device is "current limiting".
		It restricts fault currents to such low values that a high degree of protection is given to circuit components against even very high short circuit currents.
	www.pecoindustries.com /faqs.html (1384 words)

	Ferraz Shawmut: Arc Flash Resource Center \| Glossary (Site not responding. Last check: 2007-09-10)
		As current begins passing through ionized air, large volumes of ionized gases, along with metal from the vaporized conductors, are rapidly expelled, creating such hazards as intense heat, thermoacoustic shock wave, molten metal, shrapnel, blinding light, toxic smoke and contact with energized components.
		By isolating a faulted circuit before the fault current has sufficient time to reach its maximum value, a current-limiting fuse tremendously limits the total electrical energy delivered to the fault, reducing both the magnitude and duration of a fault current.
		A state in which the conductor or circuit part to be worked on or near has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if necessary.
	www.ferrazshawmut.com /arcflash/getting_help/glossary.cfm (832 words)

	:: HPL Group :: >> Products (Site not responding. Last check: 2007-09-10)
		The high-speed current limiting action ensures that the MCB operates before the full prospective fault current is allowed to develop.
		When the current flowing through the MCB reaches a predetermined level, the solenoid in Magnetic Coil directly pulls in the plunger, which forcibly separates the contacts and simultaneously release the trip mechanism.
		In the event of an over current or short circuit the MCB automatically interrupts all poles even if the MCB toggle is held in 'ON' position.
	www.hplindia.com /product6.htm (539 words)

	Industrial Electrical Maintenance Certificate
		Circuit analyses such as maximum power transfer, delta-wye conversion, mesh analysis, and Thevenin and Norton circuits will be studied.
		This course continues studies in alternating current circuits with a focus on RLC circuits.
		Phase relationships between voltage and current, and the reactive elements of alternating current circuits that contribute to industrial power factors are examined in detail.
	www.mtc.edu /Academic/iem_cert.htm (1342 words)

	Random Works of the Web » Blog Archive » High-voltage direct current (Site not responding. Last check: 2007-09-10)
		Since the flow of current through the distribution wires resulted in a voltage drop, it became difficult to regulate the voltage at the distribution circuit extremities.
		Conductor cost is roughly proportional to the current carried, and conductor loss is roughly proportional to the square of the current, so higher transmission voltages improve the efficiency of transmission.
		It should be noted that the current scientific consensus [1] does not consider ELF sources and their associated fields to be particularly harmful, and that deployment of HVDC equipment would not completely eliminate electric fields, as there would still be DC electric field gradients between the conductors and ground.
	random.dragonslife.org /high-voltage-direct-current/332 (3576 words)

	Maytum.html
		Test circuits are those depicted in Figures 2 and 3 but with additional generator feed resistors to connect the multiple ports.
		The single-output 8/20 current generator does not promote current sharing, as the generator external-current-limiting resistor is zero.
		Lack of coordination means that the current rating of a protector P2 section can be exceeded, because it carries the total current conducted by both sections of protector P1.
	www.ce-mag.com /archive/04/Maytum.html (2580 words)

	The Electricity Safety, Quality and Continuity Regulations 2002
		(c) protected by a suitable fusible cut-out or circuit breaker which is situated as close as is reasonably practicable to the supply terminals.
		(2) Every circuit breaker or cut-out fuse forming part of the fusible cut-out mentioned in paragraph (1)(c) shall be enclosed in a locked or sealed container as appropriate.
		A safety sign shall incorporate a design, and shall be of the proportions, as shown in the diagram below, except that the height of the text may be increased to a maximum of 0.12 × L. The triangle, symbol and text shall be shown in fl on a yellow background.
	www.opsi.gov.uk /si/si2002/20022665.htm (8503 words)

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