Do Littelfuse overcurrent protection fuses have self-resetting function?

Power Circuit Protection
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Question: Do Littelfuse’s overcurrent protection fuses include any self-resetting functions, to avoid having to replace fuses?
Answer: No. Overcurrent protection fuses are a one-time use device.

Principle of thermal melting

Fuses are usually made of metals or alloys with a low melting point. When the current in the circuit exceeds the rated current, the temperature of the fuse will rise rapidly due to the heat generated by the current.

This fusing process is irreversible. Once the metal of the fuse melts and breaks, its physical structure has undergone a fundamental change and cannot return to its original conducting state on its own.

We can understand the fusing capacity of a Fuses based on the T - C curve and “I²t”.

For example:

DigiKey Part Number F1710-ND
Manufacturer Littelfuse Inc.
Manufacturer Product Number 0216008.MXP
Detailed Description 8 A 250 V AC DC Fuse Cartridge, Ceramic Requires Holder 5mm x 20mm
Datasheet Datasheet

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image258×258 42.7 KB

We can find the T - C curve of this product in Datasheet

The temperature to current curve of a Littelfuse fuse.
The temperature to current curve of a Littelfuse fuse.865×608 114 KB

This curve is mainly used to illustrate the impact of ambient temperature on the device’s rating. When the ambient temperature decreases, the rated value that the device can withstand may increase; when the ambient temperature rises, the rated value that the device can withstand will decrease. This is very important for the safe operation and performance evaluation of the device under different ambient temperatures.

What is “I²t”?

“I²t” represents the square of the current multiplied by time, with the unit of Ampere-squared seconds (A² sec). Here, “I” stands for current and “t” stands for time.

  • In overcurrent protection devices (such as Fuses, the I²t value represents the energy passing through the protection device when the circuit experiences overload or short circuit. When the current in the circuit suddenly increases, the I²t value will accumulate rapidly.

  • For a given protection device (such as Fuses, it has a specific I²t rating. When the I²t value generated by the current passing through the device within a certain time reaches or exceeds this rated value, the protection device will operate (for example, the fuse will blow), thus cutting off the circuit and protecting downstream electrical equipment from damage caused by excessive current.

  • When choosing and designing a circuit protection scheme, the I²t value is an important parameter. Different electrical equipment and circuits have different overcurrent tolerance capabilities. By calculating and considering the I²t value, you can ensure that the selected protection device can operate in a timely manner at the appropriate moment, neither misoperating under normal current fluctuations nor delaying operation in the case of overcurrent, which could lead to equipment damage.

More Littelfuse circuit protection products

Littelfuse Circuit Protection products provide stable and reliable signal transmission guarantee for all kinds of precision electronic devices by virtue of their precise adjustment relationship with capacitance, dynamic resistance, etc. in terms of high-frequency characteristics, and their performance is excellent in the industry.

More Q&A on Littelfuse Circuit Protection Products Technology:

I. Questions Related to Component Characteristics

  1. What are the classifications of gas discharge tubes?

  2. Littelfuse new MOV+Sidactor thyristor vehicle charging solution technological innovations

  3. In Littelfuse circuit protection products, what kind of current is I in I²t?

  4. What are the differences between discharge tubes and metal oxide varistors?

II. Questions Related to Selection

  1. How to select metal oxide varistors for overvoltage protection?

  2. Do Littelfuse overcurrent protection fuses/circuit breakers have self-resetting function?

  3. The difference in the selection of overvoltage / overcurrent between AC and DC input terminals?

  4. When to Use PTC Resettable Fuses and Metal Fuses?

  5. What parameters differ between surface mount and through hole fuse selections?

  6. Under what general circumstances can AC components be directly used in DC circuits?

  7. Can the method of paralleling small-capacity fuses be used to achieve the purpose of fast fusing?

III. Questions Related to Applications

  1. What design requirements for overcurrent and overvoltage protection?

  2. In which fields are gas discharge tubes mainly applied? Do they have directionality?

  3. Are overcurrent and overvoltage protection for AC/DC power inputs used in charging piles?

  4. Can Littelfuse Circuit Protection Products Protect Against Overvoltage and Overcurrent?

  5. How to understand the fuse explosion-proof test?

  6. How to specifically know the time of time-delay fusing fuses?