In electronics and electrical engineeringa fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current.
It is a sacrificial device ; once a fuse has operated it is an open circuit, it must be replaced or rewired, depending on type. Fuses have been used as essential safety devices from the early days of electrical engineering. Today there are thousands of different fuse designs which have specific current and voltage ratings, breaking capacity and response times, depending on the application. The time and current operating characteristics of fuses are chosen to provide adequate protection without needless interruption.
Wiring regulations usually define a maximum fuse current rating for particular circuits. Short circuitsoverloading, mismatched loads, or device failure are the prime or some of the reasons for fuse operation.
A fuse is an automatic means of removing power from a faulty system; often abbreviated to ADS Automatic Disconnection of Supply. Circuit breakers can be used as an alternative to fuses, but have significantly different characteristics.
Breguet recommended the use of reduced-section conductors to protect telegraph stations from lightning strikes ; by melting, the smaller wires would protect apparatus and wiring inside the building.
A fuse was patented by Thomas Edison in as part of his electric distribution system. A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and usually enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow. The size and construction of the element is empirically determined so that the heat produced for a normal current does not cause the element to attain a high temperature.
If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit.
The fuse element is made of zinc, copper, silver, aluminum, [ citation needed ] or alloys [ clarification needed ] to provide stable and predictable characteristics. The element must not be damaged by minor harmless surges of current, and must not oxidize or change its behavior after possibly years of service.
The fuse elements may be shaped to increase heating effect. In large fuses, current may be divided between multiple strips of metal. A dual-element fuse may contain a metal strip that melts instantly on a short circuit, and also contain a low-melting solder joint that responds to long-term overload of low values compared to a short circuit.
Fuse elements may be supported by steel or nichrome wires, so that no strain is placed on the element, but a spring may be included to increase the speed of parting of the element fragments. The fuse element may be surrounded by air, or by materials intended to speed the quenching of the arc.
Silica sand or non-conducting liquids may be used.
The speed at which a fuse blows depends on how much current flows through it and the material of which the fuse is made. The operating time is not a fixed interval, but decreases as the current increases. Fuses have different characteristics of operating time compared to current. A standard fuse may require twice its rated current to open in one second, a fast-blow fuse may require twice its rated current to blow in 0. Fuse selection depends on the load's characteristics.
Semiconductor devices may use a fast or ultrafast fuse as semiconductor devices heat rapidly when excess current flows. The fastest blowing fuses are designed for the most sensitive electrical equipment, where even a short exposure to an overload current could be very damaging. Normal fast-blow fuses are the most general purpose fuses. A time-delay fuse also known as an anti-surge or slow-blow fuse is designed to allow a current which is above the rated value of the fuse to flow for a short period of time without the fuse blowing.
These types of fuse are used on equipment such as motors, which can draw larger than normal currents for up to several seconds while coming up to speed. Manufacturers can provide a plot of current vs time, often plotted on logarithmic scales, to characterize the device and to allow comparison with the characteristics of protective devices upstream and downstream of the fuse.Each circuit in the home is protected by a fuse, and each fuse must be the correct type and have an appropriate amperage rating for its circuit.
Using the wrong type of fuse for a circuit can pose a serious fire hazard, so it's important to identify the correct fuse for each circuit. Fuses for standard circuits not high-voltage appliance circuits are called plug fuses and have screw-in bases. There are two different types of bases and screw-in fuses: the Edison base found on Type T fuses and the rejection base found on Type S fuses.
Rejection base Type S fuses will work with Edison-type sockets only when combined with an adapter base that screws and locks into the Edison socket. The Type S fuse then screws into the adapter. Rejection bases are also known as "tamper-proof," and they were developed to prevent homeowners from using the wrong type of fuse for a circuit. Each Type S fuse of a specific amperage rating has a matching base adapter with a specific size of thread that prevents mismatching the fuses.
For example, it stops a person from putting a amp fuse in a amp circuit, a potentially serious mistake. A amp Type S fits only a amp base adapter. By contrast, a Type T fuse can fit into any Edison socket, regardless of the circuit's amperage. They are general-purpose plug fuses and are "fast-acting"—that is, they have no time-delay fuse element and quickly interrupt the circuit once the fuse's rated amperage is exceeded.
These fuses are designed for use in general lighting and power circuits that do not contain electric motors. Electric motors draw additional current at startup and will blow a Type W fuse if the motor is of any significant size. Because of this, time-delay fuses are used much more commonly than type-W fuses. Type-W fuse rating: volts; up to 30 amps. SL and TL fuses are medium-duty time-delay fuses and are now the most commonly used plug fuses found in home electrical systems. Without a time-delay feature, simply starting your garbage disposer or refrigerator would cause a fuse to blow.
Type SL and TL fuse rating: volts; up to 30 amps. These fuses have a longer time-delay feature than the SL or TL fuses. However, just like the SL and TL fuses, the only difference between the S and the T heavy-duty fuses are the bases: type-S has a rejection base; type-T has an Edison base.
Heavy-duty time-delay fuses contain a spring-loaded metal fuse link attached to a solder plug. If the overloaded circuit condition continues for too long, the solder plug melts and the spring pulls the fuse link free, cutting power to the circuit.In the US, the standard for general those not feeding a specific load, like a stove or dryer branch circuit is 15 amps although sometimes 20 amps is used.
In addition, there are branch circuits for the stove, dryer, air conditioning, etc. The thing to note is that the sum of all the branch circuits is greater than the ampacity of the service entrance. The difference between the two is based on the assumption that not all of the branch circuits will be drawing their full rated current at all times.
The branch circuit breakers protect their wiring against overloads, and the main breakers protect the supply and panel against overloads. This same philosophy is duplicated in generally commercial buildings where there are sub-panels closer to the loads. There will be a master breaker for the sub-panel, generally located at the source panel for the supply to the sub-panel, but sometimes at the sub-panel itself. One type, a burning fuse, rarely used anymore, is used to detonate explosives.
After being lit, the fuse burns its way to the charge, allowing the initiator enough time to move to a safe distance.
Another type of fuse short for "fusible link"in an electrical circuit, acts as a safety device, guarding the circuit against a current over-load carrying more current than it was designed for. If an electrical over-load occurs, the fuse melts in a controlled fashioncausing an "open or break " in the circuit, thus protecting the circuit by stopping current flow through it.
An open or broken circuit is an incomplete circuit, which current cannot pass through. The currant over-load is headed off at the fuse. Once the reason for the over-load has been found and repaired, the fuse now melted which is needed to complete the circuit, must be replaced in order to restore normal function.
The fuse is lost but is very cheap and easy to replace. The circuit, which the fuse has protected, would have been much more expensive to repair, as would be the damage caused by a fire, a likely consequence of an un-fused overloaded circuit.
His job was to get gun powder, move it to Parliament And light the fuse to blow up Parliament. The main role of the jury is to decide if the defendant is guilty or innocent. It serves as the final authority to resolve issues with domestic policies. There is no main role everyone does their share either shooting, attacking or defending There is no main role everyone does their share either shooting, attacking or defending There is no main role everyone does their share either shooting, attacking or defending.
The role of most of them was to raise the children, do domestic chores and make a home for their families. Voltage doesn't move through anything. It's pressure or potential.
A Guide to Screw-In Fuses
Current, however, is the flow of electrons, and this is what a resistor limits. Without a correctly sized resistor, the unchecked current will kill the LED. Insulators are used to keep electrical currents in the circuit. If they do not follow the entire circuit, it would be a "short circuit". The main role of the Federalist Papers was to raise support for the ratification of the Constitution.
Ferrets are Domestic pets and have no role in the food web. They totally rely on humans for survival. There is one thing that a cell does in an electric circuit. The function of a cell is to supply energy.
Asked By Curt Eichmann.House Wiring for Beginners gives an overview of a typical basic domestic mains wiring system, then discusses or links to the common options and extras. Further information on options is available in the Rewiring Tips article.
Calculating Electrical Load Capacity for a Home
For these reasons and more, one should not carry out safety critical work based solely on wiki content. Information and plans should be independently checked and verified before action. Anyone installing wiring should also understand some basic safety issues not discussed here. This article is an introductory overview rather than a complete A to Z on rewiringand assumes some basic electrical knowledge.
Some regulatory requirements are mentioned in this article. These apply to new wiring, and in many cases are not requirements for existing wiring. The Electrical Glossary may be useful. The radial lighting circuit has 3 common wiring options, which may be mixed at will:. Other options are also possible:. Each fuse or MCB supplies one circuit only. One circuit may supply anything from 1 to a large number of loads.
Split load CUs have become popular in recent years, and ubiquitous since with the introduction of the 17th edition of the wiring regs.
They usually offer significant advantages over the traditional unsplit CU type. See 17th Edition Consumer Units for more details. Each bank usually having its own RCD. There should also be a master switch that will switch the whole CU. Split load CUs are recommended, and this article will assume the use of a split load CU. Earthing is a fundamental safety system used in electrical installations. It works in co-ordination with circuit breakers MCBsFusesand RCDs to ensure that an electrical supply can be disconnected quickly in the event of a fault.
This greatly reduces shock risk. Most houses have an earth connection supplied by the electricity supplier. Those that don't generally country houses several miles from the nearest townuse a local earth rod instead. The supplier's earthing terminal or your own earth rod is connected to the CU earth block.
Each electrical circuit in the house takes its earth connection from the CU earthing block. In general, ANY cable which is buried less than 50mm below a wall's surface AND is NOT mechanically protected, or wired in one of a number of specialised cable types that incorporate an earthed screen must have 30mA trip RCD protection. New installations will have two or more RCDs. Older ones may only have one or none.
RCDs reduce the risks of injury from electric shock they don't eliminate it completelyhowever they can also introduce reliability and issues of their own if not used in an appropriate way. Historically RCDs were usually only used on some circuits rather than all. With a local earth rodthe situation is different in that all circuits must be RCD protected, since a local earth rod is not usually a sufficiently good earth on its own to clear all earth faults. So RCDs are used on all circuits even in older installations.
This is not an ideal arrangement, as a large earth leakage fault on the non-RCD side will cause complete power failure, and sometimes inability to reset the power. RCBOs allow individual circuits to be protected by their own RCD without any risk that a fault in an unrelated circuit could cause it to trip. However protecting all circuits like this is more expensive.Understanding capacity and load becomes necessary if you are planning the electrical service for a new home, or if you are considering an electrical service upgrade to an older home.How to set empty value in xslt
Understanding the load needs will let you choose an electrical service with an appropriate capacity. In older homes, it's extremely common for the existing service to be badly undersized for the needs of all the modern appliances and features now in use. The term " electrical load capacity" refers to the total amount of power provided by the main service for use by your home's branch circuits and the lights, outlets, and appliances connected to them.
Total electrical capacity of an electrical service is measured in amperage amps. In very old homes with knob-and-tube wiring and screw-in fusesyou may find the original electrical service delivers 30 amps. Slightly newer homes built before may have amp service.
In many homes built after or upgraded older homesamps is the standard service size. But in large, newer homes, amp service is now as a minimum, and at the very top end, you may see amp electrical service installed.
How do you know if your current electrical service is adequate, or how do you plan for new electrical service?
Determining this requires a little math to compare total available capacity against the likely load that will be placed on that capacity. Calculating how much power your home needs is a matter of calculating the amperage load of all the various appliances and fixtures, then building in a margin of safety.
Generally, it's recommended that the load never exceeds 80 percent of the electrical service's capacity. To use the math, you need to understand the relationship between watts, volts, and amps.
These three common electrical terms have a mathematical relationship that can be expressed in a couple of different ways:. These formulas can be used to calculate the capacity and loads of individual circuits, as well as for the entire electrical service.
For example, a amp, volt branch circuit has a total capacity of 2, watts 20 amps x volts.Mustang models
Since the standard recommendation is for the load to total no more than 80 percent of the capacity, this means that the amp circuit has a realistic capacity of watts.
So to avoid the danger of overloads, all the light fixtures and plug-in appliances together on this circuit should consume no more than 1, watts of power. It is fairly easy to read the wattage ratings of all the lightbulbs, television sets, and other appliances on the circuit to determine if a circuit is likely to overload.
For example, if you routinely plug a watt space heater into a circuit, and run several light fixtures or lamps with watt bulbs on the same circuit, you have already used up most of the safe watt capacity. The same formula can be used to determine the capacity of the house's overall electrical service. Because a home's main service is volts, the math looks like this:. In other words, a amp electrical service should be expected to provide no more than 19, watts of power load at any given time.
After you know the capacity of individual circuits and of the home's full electrical service, you can then compare this with the load, which you can calculate simply by adding up the wattage ratings of all the various fixtures and appliances that will be drawing power at the same time. You might think this involves adding up the wattage of all the light fixture lightbulbs, all the plug-in appliances, and all the hard-wired appliances, and then comparing this to the total capacity.
But it is rare for all electrical appliances and fixtures to run at the same time—you wouldn't run the furnace and the air conditioner at the same time, for example; nor is it be likely that you would be vacuuming while the toaster is running.What is Ground? Earth Ground/Earthing
For this reason, professional electricians generally have alternative methods for determining the appropriate size for the electrical service.The fuses are held by spring metal clipsthe clips are themselves being permanently connected to the circuit conductors.
Yes, the electric windows are connected to a circuit protection devise such as a fuse or circuit breaker. A fuse is connected in series with the load. For safety reasons, it is always placed in the line conductor, never in the neutral conductor. A fuse is an over current protection device, and will operate wherever it is placed in a circuit. However, because it's important that it isolates the faulty circuit from the supply, it MUST be located in the line NEVER the neutral conductor at the point where the circuit is connected to the supply.
The point is that the circuit will always be energised and potentially dangerous up to the point where the fuse is connected, even when the fuse has operated and no current can flow. If you were to connect a fuse or circuit breaker in parallel with a circuit, it would create a short circuit and immediately melt fuse or trip circuit breaker. These devices must be connected in series with the load. Because if it is not connected to both it is not a full circuit and therefore if it is not a full circuit then the fuse can't protect you.
The fuse is in series between the hot side of supply voltage and the circuit or device. It depends on where the over current protection is located in the circuit. If the protection is the first device in the circuit everything connected to the circuit will stop operating.
If a connected device has its own protection and that device faults that fuse will disconnect the device but the rest of the circuit will remain on. Just remember that the lowest rated fuse in a circuit will open first in a fault condition. No, the one amp fuse is the recommendation of the manufacturer of the circuit. By replacing it with a fuse five times larger will default the warranty placed on the equipment by the manufacturer. Where one amp will do no damage to the circuit, five amps could destroy the components that are connected in the circuit.Call philippines
Fuse is a circuit element which disconnects the electrical current from the mains"supply" feeding the load when a condition of fault "short circuit " occurs. Absolutely not. A fuse works by "monitoring" the current flowing in the circuit. Setting the fuse next to whatever it should be monitoring will do absolutely no good.Tropical fish minecraft
If the circuit is a single wire circuit and the fuse blows the circuit will open. If the circuit is a three wire circuit and the fuse blows in a neutral, then there is a possibility of the two circuits becoming in series with each other and if the load is not balanced one circuit can become overloaded. It is exactly the reason why in North America the electrical code does not allow the fusing of any neutrals.Normally, the ampacity rating of a conductor is a circuit design limit never to be intentionally exceeded, but there is an application where ampacity exceedance is expected: in the case of fuses.
A fuse is an electrical safety device built around a conductive strip that is designed to melt and separate in the event of excessive current. Fuses are always connected in series with the component s to be protected from overcurrent, so that when the fuse blows opens it will open the entire circuit and stop current through the component s. A fuse connected in one branch of a parallel circuitof course, would not affect current through any of the other branches. Normally, the thin piece of fuse wire is contained within a safety sheath to minimize hazards of arc blast if the wire burns open with violent force, as can happen in the case of severe overcurrents.
Domestic Electric Circuit
In the case of small automotive fuses, the sheath is transparent so that the fusible element can be visually inspected. Residential wiring used to commonly employ screw-in fuses with glass bodies and a thin, narrow metal foil strip in the middle.
A photograph showing both types of fuses is shown here:. Cartridge type fuses are popular in automotive applications, and in industrial applications when constructed with sheath materials other than glass. This means they will be inserted into some type of holder rather than being directly soldered or bolted to the circuit conductors.
The following is a photograph showing a couple of glass cartridge fuses in a multi-fuse holder:. The fuses are held by spring metal clips, the clips themselves being permanently connected to the circuit conductors. The base material of the fuse holder or fuse block as they are sometimes called is chosen to be a good insulator. Another type of fuse holder for cartridge-type fuses is commonly used for installation in equipment control panels, where it is desirable to conceal all electrical contact points from human contact.
Unlike the fuse block just shown, where all the metal clips are openly exposed, this type of fuse holder completely encloses the fuse in an insulating housing:. The most common device in use for overcurrent protection in high-current circuits today is the circuit breaker. Circuit breakers are specially designed switches that automatically open to stop current in the event of an overcurrent condition. Small circuit breakers, such as those used in residential, commercial and light industrial service are thermally operated.
They contain a bimetallic strip a thin strip of two metals bonded back-to-back carrying circuit current, which bends when heated. When enough force is generated by the bimetallic strip due to overcurrent heating of the stripthe trip mechanism is actuated and the breaker will open.
Larger circuit breakers are automatically actuated by the strength of the magnetic field produced by current-carrying conductors within the breaker, or can be triggered to trip by external devices monitoring the circuit current those devices being called protective relays. A photograph of a small circuit breaker is shown here:. From outside appearances, it looks like nothing more than a switch.
Indeed, it could be used as such. However, its true function is to operate as an overcurrent protection device. It should be noted that some automobiles use inexpensive devices known as fusible links for overcurrent protection in the battery charging circuit, due to the expense of a properly-rated fuse and holder.
A fusible link is a primitive fuse, being nothing more than a short piece of rubber-insulated wire designed to melt open in the event of overcurrent, with no hard sheathing of any kind. Such crude and potentially dangerous devices are never used in industry or even residential power use, mainly due to the greater voltage and current levels encountered. As far as this author is concerned, their application even in automotive circuits is questionable.
Fuses are primarily rated, as one might expect, in the unit for current: amps. This is largely accomplished by making the fuse wire as short as is practically possible. Since length is not a factor in current rating, the shorter it can be made, the less resistance it will have end-to-end. However, the fuse designer also has to consider what happens after a fuse blows: the melted ends of the once-continuous wire will be separated by an air gap, with full supply voltage between the ends.
Consequently, fuses are rated in terms of their voltage capacity as well as the current level at which they will blow. Some large industrial fuses have replaceable wire elements, to reduce the expense.
The body of the fuse is an opaque, reusable cartridge, shielding the fuse wire from exposure and shielding surrounding objects from the fuse wire. If a current of 35 amps is sent through a 30 amp fuse, it may blow suddenly or delay before blowing, depending on other aspects of its design.
The latter fuses are sometimes called slow-blow fuses due to their intentional time-delay characteristics. A classic example of a slow-blow fuse application is in electric motor protection, where inrush currents of up to ten times normal operating current are commonly experienced every time the motor is started from a dead stop.Invitation letter to join a new school
If fast-blowing fuses were to be used in an application like this, the motor could never get started because the normal inrush current levels would blow the fuse s immediately!
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