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Current Limiting Fuse VS Expulsion Fuse

Time:2023-12-04   Author:As Beam   Browse:

Electrical protection is crucial in safeguarding systems against potential hazards. Among the various types of protective devices, fuses play a pivotal role. This article delves into comparing two significant types of fuses: the current limiting fuse and the expulsion fuse.


What is Current Limiting Fuse?


A Current Limiting Fuse (CLF) is a type of electrical safety device designed to protect electrical circuits and equipment from excessive currents. Its primary function is to limit the amount of current that flows through a circuit during a fault or overload condition.

 Mersen Current Limiting Fuse.jpg

How does Current Limiting Fuse works?


Current limiting fuses operate on the principle of restricting excessive currents within a circuit. By promptly interrupting the flow of current when it surpasses a predefined limit, these fuses prevent damage to the system. Their ability to curtail fault currents swiftly makes them ideal for high-power applications, ensuring minimal disruption and damage.


One of the key advantages of current limiting fuses lies in their ability to swiftly mitigate fault currents, thereby reducing stress on the system components. Real-world applications often showcase their effectiveness in safeguarding sensitive equipment.

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Expulsion Fuse


In contrast, expulsion fuses operate by expelling gases to extinguish an arc formed during a fault. They are effective in interrupting high currents and clearing faults. These fuses find applications in various scenarios where their ability to handle higher fault currents is essential.


Expulsion fuses, also known as power fuses or boric-acid fuses, are types of high-voltage fuses primarily used in electrical power distribution systems. These fuses are designed to protect electrical circuits against over current conditions, such as short circuits and overloads.

Eaton Expulsion Fuse.jpg


The distinguishing feature of expulsion fuses is their ability to vent or expel gases when interrupting a fault current. When a fault occurs, the current passing through the fuse increases dramatically. This surge in current causes the fuse element to melt or vaporize rapidly. As the fuse element disintegrates, it creates an arc.


The arc formed during the interruption process is a potential hazard because it can sustain itself and continue conducting current. To prevent this, expulsion fuses are designed with mechanisms to quickly extinguish the arc. Boric acid, often contained within the fuse assembly, plays a crucial role in this process.


When the arc forms inside the fuse, the boric acid interacts with the gases produced by the arc. This interaction leads to the creation of gases that help extinguish the arc by rapidly cooling and deionizing the gases within the arc path. Additionally, the pressure created by these gases aids in forcefully expelling the gases and suppressing the arc.


The expulsion process helps to quickly interrupt the current flow, preventing sustained arcing and protecting the electrical system from damage.


Expulsion fuses excel in scenarios demanding higher fault current interrupting capacities. Their mechanism of operation involves creating a controlled arc to prevent damage, making them suitable for specific industrial settings.


Current Limiting Fuses and Expulsion Fuses Performance Comparison


Comparing the performance of these two types of fuses is essential for selecting the right one for a given scenario. Factors such as safety, cost, and response times play significant roles in determining their suitability.


While current limiting fuses excel in swift response and protecting equipment, expulsion fuses stand out in handling higher fault currents with controlled arc interruption. Depending on the specific requirements of an application, one may be more suitable than the other.

Eaton Current Limiting Fuse.png



Current Limiting Fuses and Expulsion Fuses serve distinct functions in electrical systems and have different operating mechanisms. Here's a comparison of their performance:




Current Limiting Fuses are designed to limit the amount of current flowing through a circuit during a fault or overload condition. They aim to quickly interrupt excessive currents to protect equipment and prevent damage.

Expulsion Fuses are primarily used to interrupt high fault currents by creating a controlled arc and then extinguishing it through the release of gases (like boric acid) to rapidly cool and deionize the arc path.


Interrupting Capacity:


Current Limiting Fuses have excellent current-limiting capabilities. They swiftly interrupt high fault currents, limiting the potential damage to the system and connected equipment.

Expulsion Fuses are also effective in interrupting high currents by venting gases to extinguish the arc. However, their primary focus is on interrupting the arc and preventing sustained arcing.


Arc Extinction:


Current Limiting Fuses limit the fault current and can extinguish arcs, but their primary function isn’t specifically focused on arc extinction.

Expulsion Fuses are explicitly designed to handle the arc extinction process by releasing gases that cool and deionize the arc.

Arc Extinction.jpg




Current Limiting Fuses are commonly used in various applications where protection against short circuits and overloads is critical, such as industrial settings, power distribution systems, and electrical equipment.


Expulsion Fuses find their applications in high-voltage systems, especially in power distribution and substations, where interrupting high fault currents and preventing sustained arcs is essential.


Response Time:


Both types of fuses generally have fast response times. Current Limiting Fuses quickly limit the current, while expulsion fuses rapidly create and extinguish arcs to interrupt the flow of high currents.


Maintenance and Replacement:


Both Current Limiting Fuses and expulsion fuses, when operated under normal conditions, don't require frequent maintenance. However, after a fault occurrence, they often need replacement.

In summary, Current Limiting Fuses are primarily focused on limiting current during faults, while expulsion fuses specialize in interrupting high fault currents by creating and rapidly extinguishing arcs through gas release. Their specific design and functionality cater to different aspects of electrical system protection, with some overlap in their ability to handle fault currents. Their selection depends on the specific needs and requirements of the electrical system.

Fuse Replace.jpg


Current Limiting fuse types

( There are 3.6KV, 7.2KV, 12KV, 15.5KV, 17.5KV, 24KV, 35KV, 36KV, 40.5KV level fuses. More detail visit: “What's Current Limiting fuse types?” )


In conclusion, the choice between a current limiting fuse and an expulsion fuse hinges on specific operational needs. Each has its distinct advantages and applications. A thorough understanding of their mechanisms and performance in varied scenarios is crucial for selecting the most suitable option.


Ultimately, both types of fuses serve the fundamental purpose of protecting electrical systems, albeit with differences in their operational mechanisms and capabilities.

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TAG:   Current Limiting Fuse Expulsion Fuse