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For most of us who work in the electrical design field, the question of circuit protection is omnipresent in our day-to-day efforts. There are a myriad of circuit protection technologies available that address phenomenon such as high voltage transients, inductive kick-back, capacitive coupling, high inrush currents and ground faults, just to name a few.

However, the most common circuit protection devices guard against over-current situations. As most of us already know, over-current protection is typically achieved by incorporating either a fuse or a circuit breaker within the primary power feed. The biggest question that faces most electrical designers is which one of these devices to select for any given situation.

More often than not, our selection of either fuses or circuit breakers is based on past experience and personal preference. In the context of any given industry, past experience is usually a good guide for this selection process. However, when changing projects or moving to a new job, what may be comfortable to you, may not be appropriate for the new application.

So what criteria do we use to select one or the other? The recurring argument that I have heard in favor of circuit breakers is that they are easier to reset after a failure situation has occurred. In these situations, the convenience of resetting the breaker only serves to postpone the inevitable correction or re-design of the circuit.

On the other side of the fence, the usual argument in favor of fuses is that they are dirt cheap. However, if a circuit blows fuses on a regular basis, the accumulated replacement costs associated with labor and down time can make a fuse set considerably more expensive over the long run. Additionally, if a fuse set is specified as an integral part of a power disconnect, then the cost is comparable to the equivalent circuit breaker arrangement.

It should come as no surprise that both fuses and circuit breakers have their pros and cons. Circuit breakers certainly have some very favorable attributes.

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Another attractive attribute of breakers is that they are inherently safe. The electrical connections are typically located behind a protective panel, which completely eliminates any possibility of electrocution.

This feature is quite valuable, especially in those situations when non-electrical personnel are required to service the equipment. A third feature is that they usually provide a visual indicator when they have tripped. For many professionals, fuse sets also have a number of desirable attributes. As mentioned previously, they are particularly inexpensive when compared to their breaker counterparts.

Wires are usually connected with integral screw-type terminal blocks. In addition to their mechanical simplicity, the electrical flexibility that fuses provide can be a considerable asset, especially when working with unique circuits.

In these cases, the selected fuse can be quickly changed for another unit that is better suited for the application. A good example of this is a machine that has a high power-up surge current. The original fuse specified may be quite adequate for the run current, but may blow each time the circuit is energized. A fuse set allows the technician to quickly correct the situation at the minimal cost of a few new fuses.

The original fuses are simply replaced with time delay, or slow-blow, units carrying the same current rating and the problem is instantaneously corrected.

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In that case, the breaker must be removed and replaced with an entirely new unit with a rating appropriate to the conditions. The costs associated with a change like this are reflective of a new breaker and the labor to remove the old unit and replace it with the new one.

A significant disadvantage of fuse sets is their exposed electrical connections. In the case of larger, snap-in fuses, the socket clips are exposed and in close proximity to the opposite side s of the circuit.

When the enclosure housing the fuse set is opened, these sockets expose the technician to a live circuit. Many power disconnects with integral fuse sets are specifically designed to eliminate this hazard when turned off.

However, in a pinch, the average technician will be under a lot of pressure to get the equipment operational. There is simply no future in these improper practices, which will ultimately lead to an electrocution incident.Electrical Academia. Generally, the circuits supplying electric motors should be protected against overload and fault currents. In addition, any unattended motor should be protected against:. There is also the requirement that all electric motors must have a control device for stopping and starting and an isolator.

All of the above requirements are usually met by installing fuses or circuit breakers in the switchboard, an electric motor starter with controls at a convenient location and an isolator near the electric motor. Modern proprietary motor starters are available with any, or all, of the above requirements built into the one unit.

The fuse is possibly the simplest form of circuit protection. It consists of a fuse element designed to melt and prevent further current flow.

fuses and circuit breakers protect against overcurrent

The major disadvantage of a blown fuse is that the active component has to be replaced. The primary purpose of a fuse is to protect a circuit rather than any load. Under short-circuit conditions the reaction time of an HRC fuse in isolating a circuit is probably the fastest of all protection systems.

A fuse element has to have a current rating high enough to allow an electric motor to draw starting currents, yet low enough to give some protection against overloads. Because of these opposing factors, a fuse cannot provide complete protection for both the circuit and the load.

fuses and circuit breakers protect against overcurrent

They have a plastic carrier and base and are designed to be used with enclosed fuse links. HRC fuses are extremely consistent and reliable in terms of tripping values. The element of an HRC fuse is enclosed in an insulating tube filled with powdered quartz to quench any arc that might develop. Figure 1 HRC fuses for three-phase electric motor circuit. This type has lugs to allow the fuse link to be held in place with machine-threaded screws.

HRC fuses up to 63 A are often manufactured with plug-in fuse links. Figure 2 Cutaway view of a cartridge for an HRC fuse. The silver element has restrictions cut into its section in order to give a very fast response to fault currents. This gives the HRC fuse a very fast response time to fault currents. The fuse element of an HRC fuse has a eutectic bead to give a good response to prolonged overload currents. If a prolonged overload current flows, the eutectic bead will reach a point where it can no longer dissipate the heat and will melt.

To ensure the safe operation of equipment, it is essential that only the correct size be used when replacing HRC fuses. Replacement cartridges of the correct size should be kept on hand for all HRC fuses. These are capable of providing protection while not tripping on motor-starting currents.It is made of porcelain, glass or porcelain. The fuse link or fuse element is a thing metal strip made up of Copper, Silver, Aluminum, Zinc, or alloys.

When overload occurs, the fuse element starts to melt immediately and break the connected circuit from the incoming supply. Thus, it protects the whole circuit. In circuit breaker, electromechanical switch and relay mechanism trip the circuit when an unsafe value of current overload or short circuit attempts to flow in the circuit connected through circuit breaker.

This way, it protect the connected circuit by discounting it from power supply during faults such as overload or short circuit currents. Bothe Fuse and Circuit breaker are rated in Amperes which can be seen on its nameplate which is known as Rated Current or Nominal Current.

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We know that both fuse and circuit breaker having the same rated current say 30A will not trip when more than 30A say 32 is flowing through them. But there is a big difference between fuse and circuit breaker i.

One of the main differences between circuit breaker and fuse is that a 30A rated current for both fuse and circuit breaker, a fuse need A and circuit breaker need A for tripping in 0. It shows very high difference in amperes. Keep in mind that the full load current of the circuit which has to be protected by fuse should not more than the fuse current rating. Fuse and circuit breaker rating and selection is depends on multiple factors.

As a general, we have to use the following formula to select proper fuse rating. For example, we have to find the circuit breaker of fuse rating in ampere for 10A two pin socket where the load is 1kW and supply voltage is V AC V in US.

Circuit breaker can be reset like simple ON-OFF switch after an automatic operation while fuse should be replaced for post-of operation. One of the major advantages of circuit breaker over fuse is that a circuit breaker can be multiple poles.

It can protect multiple lines whereas fuse is a single pole and can be used on single line. At all, as compared to fuse, a circuit breaker responds quicker, reliable in operation, and more sensitive. Your email address will not be published. Table of Contents. Electrical Technology 0 5 minutes read.

Show More.Fuses, breakers and Ground Fault Circuit Interrupters all protect circuits. Fuses or circuit breakers are added to circuits to limit the current. This allows the current to stay within the amperage rating of the conductors, that takes the supply voltage to the load.

Motor Branch Circuit Short Circuit And Ground Fault Protection (13min:31sec)

Each device has its own special use. Glass fuses can protect circuit at very low amperages. They are usually used to protect printed circuit boards and control panel circuits. Breakers protect circuits from short circuits and overloads. These devices are used in service distribution panels to protect the wires that feed the loads.

Circuit breakers can be from 15 amps up into the thousands of amps. Fuses or circuit breakers are termed 'overcurrent protection devices', which protect circuits from either an overload current or a short-circuit current. During an electrical fault, be it a short circuit or circuit overload, fuses and breakers are designed to open at a specific amperage.

This opening of either device eliminates a fire hazard before it gets a chance to start. This is how fuses and breakers protect the home. Fuses and Circuit Breakers act as a control mechanism to the flow of current in electrical circuits. A fault can develop in an electrical appliance without us noticing and this is where circuit breakers and fuses help in automatically disconnecting the faulty appliance from the power source.

Most electrical faults resulting excess heat generation which in turn cause fires. These breakers operate whenever there is an earth leakage protecting humans.

Two examples of how to protect against circuit failure are fuses and circuit breakers. Yes and No. Circuit breakers, fuses, and switches all interrupt power flow when opened.

Circuit breakers and fuses are current limiting devices that are designed to protect the wiring. They typically are tripped, or blown which automatically causes the circuit to be opened.

Circuit breakers and fuses should not be used as switches. Switches are designed to only interrupt power flow. Fuses and circuit breakers do not protect a person from electrocution. They are in the circuit to protect the feeder conductors from having over current applied to them. The only type of breaker that will protect you from getting a shock is a GFCI.

Understanding the Meaing of Overcurrent in Electrical Circuitry

The way that fuses and breakers stop household fires is by opening the fault current on the circuit before the fault temperature can rise high enough to ignite any surrounding combustible materials.

Fuses and circuit breakers are overcurrent protection devices, which means that they are designed to protect a circuit against either an overload current too much load or a short-circuit fault. Fuses do not protect a circuit against a high voltage. They shut off the power to protect the equipment circuits, the main circuits and people. Parallel circuits are not fuses.

Fuses can be used to protect parallel circuits. Circuit breakers do the same thing as fuses. They interrupt current flow when a certain preset point is reached.

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The difference between circuit breakers and fuses are that circuit breakers are resettable and reusable, whereas fuses are one time devices that must be replaced after they blow. Asked By Curt Eichmann. Asked By Leland Grant. Asked By Veronica Wilkinson.

Asked By Daija Kreiger.Overcurrent is just like it sounds: It's an excess of current—or amperage—in an electrical circuit. Circuit breakers and fuses protect circuit wiring from damage caused by overcurrent. Circuit breakers and fuses are two types of overcurrent protection devices or OCPDs.

Every electrical circuit in a home must be protected by its own OCPD that is properly rated for the circuit wiring.

Most homes today have circuit breakers, located in the home's main service panel, or "breaker box. Fuses work just as well as breakers, but like breakers, they must be properly sized for each circuit to protect against overcurrent.

If you've ever plugged in too many holiday lights in the same outlet and caused the breaker to trip, you've overloaded the circuit. Another common type of overload is a surge power draw.

This happens when a large motor, such as a refrigerator compressor, draws a surge of power to start up. If the circuit capacity is exceeded for more than a brief moment, it can trip the breaker. Circuits are usually designed to handle motor startup, and the motor's demand, or load, goes down after startup, but in some cases, it's still too much for the circuit.

Shorts can also happen if there is a break in a wire in the circuit. The short circuit path has lower resistance the normal path of the circuit, allowing a great deal of current to flow through the short path, overheating the wires. Ground faults and arc faults are similar to short circuits but have their own characteristics.

A ground fault commonly occurs when a hot wire contacts a grounded object, such as a metal electrical box when it is installed as part of a grounding system or the metal case of a tool or appliance.

Main Difference between Fuse and Circuit Breaker

This is an overcurrent situation that can energize the grounded object and deliver a dangerous shock. An arc fault is an electric discharge that jumps from one conductor to another. This can happen when a hot wire has a small break in it and makes contact only intermittently or when a hot wire touches a neutral or ground wire.

A loose wire connection on an outlet or another device also can cause arcing. Arc faults create high current flow and tremendous amounts of heat, which can melt wire insulation or start fires. Warning This is an overcurrent situation that can energize the grounded object and deliver a dangerous shock. Related Topics. Read More.To cope, CIOs in end-user organizations must learn to develop an appropriate pace for digital change.

fuses and circuit breakers protect against overcurrent

Reappraisal of the models climate scientists use to determine future warming has revealed that less optimistic estimates are more realistic. The results suggest that the Paris Climate Agreement, which aims to keep global average temperatures from rising by 2C, may be overly ambitious. Amid a flood in Islampur, Jamalpur, Bangladesh, a woman on a raft searches for somewhere dry to take shelter.

Bangladesh is one of the most vulnerable places in the world to sea level rise, which is expected to make tens of millions of people homeless by 2050. Hanna Petursdottir examines a cave inside the Svinafellsjokull glacier in Iceland, which she said had been growing rapidly.

Since 2000, the size of glaciers on Iceland has reduced by 12 per cent. Floods destroyed eight bridges and ruined crops such as wheat, maize and peas in the Karimabad valley in northern Pakistan, a mountainous region with many glaciers. In many parts of the world, glaciers have been in retreat, creating dangerously large lakes that can cause devastating flooding when the banks break.

Climate change can also increase rainfall in some areas, while bringing drought to others. A river once flowed along the depression in the dry earth of this part of Bangladesh, but it has disappeared amid rising temperatures.

Sindh province in Pakistan has experienced a grim mix of two consequences of climate change. Crops are very difficult to grow. The region has been badly affected by heatwaves and drought, making local people nervous about further predicted increases in temperature. A factory in China is shrouded by a haze of air pollution. Water levels in reservoirs, like this one in Gers, France, have been getting perilously low in areas across the world affected by drought, forcing authorities to introduce water restrictions.

Climate models are vital tools for scientists attempting to understand the impacts of greenhouse-gas emissions.

fuses and circuit breakers protect against overcurrent

But the climate system is incredibly complex, and as a result there is disagreement about how best to model key aspects of it. This means scientists have produced dozens of climate models predicting a range of different global warming outcomes resulting from greenhouse-gas emissions.

To do this, Dr Caldeira and his collaborator Dr Patrick Brown reasoned that the most accurate models would be the ones that were best at simulating climate patterns in the recent past. Their conclusion was that models with higher estimates were more likely to be accurate, with the most likely degree of warming 0. The research by Dr Brown and Dr Caldeira focuses specifically on models of energy flow from Earth to space, as measured by satellites.

They suggest that the amount of sunlight reflected away from the planet by clouds will decrease as the world gets warmer, increasing the magnitude of climate change. However, experts also warn that there is need for caution when predicting such complex phenomena as climate change.Have loved using this software on our Have loved using this software on our computers and phones.

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