Fuses protect electrical devices and components from overcurrents and short circuits that occur in improperly operating circuits.

When fault current reaches a predetermined magnitude for a fixed period of time, current flow is interrupted through the melting of an internal element.

Types of Fuses

• Miniature - Miniature cartridge fuses are commonly available in dimensions of 5x20mm and 6.3x32mm. 
• Subminiature - Also called microfuses, subminiature fuses have very small dimensions (no principal dimension greater than 10 mm) and are ideal for compact circuit board layouts.
• Midget - Midget refers to 13/32" diameter fuses.
• Automotive - Automotive fuses are specifically for use in automobiles.
• Blade type - Blade-type fuses are typically used in low voltage, high current applications.

• PC board - PC board fuses are specifically for use on PC boards.

• Protective - Protective fuses are used for protection of secondary circuits or low voltage ICs.

Specifications
 

Ratings

• Voltage rating - The voltage rating of the fuse is the maximum voltage up to which a safe fault current interruption will occur. Consider the maximum effective operating voltage of the circuit.
• Current rating - The rated current of the fuse should consider the maximum continuous operating current of the circuit and the influence of the ambient temperature. 
• Breaking capacity rating - The rated breaking capacity of the fuse (interrupting rating) is the short circuit current at which the fuse can blow (at the rated voltage) without destruction or arcing being maintained. Consider the maximum possible fault current. 
• Interrupt rating - Interrupt ratings can be high interrupt, medium interrupt, or low interrupt. 

Features

• Fast acting - Quick-acting fuses are typically used in circuits with small inrush currents or where overcurrent or short circuit must be quickly interrupted, such as resistive loads. 
• Time lag - Time-delay fuses are used where high starting inrush currents will occur and decay gradually, such as inductive or capacitive loads. 
• Environmental parameters - Important environmental parameters to consider when specifying fuse holders include operating temperature.
• Resettable - Resettable (polymeric or positive temperature coefficient - PTC) fuses are unlike traditional fuses that have to be replaced after a fault condition, this may not be necessary when using resettable fuses. The internal resistance of the component increases in response to an overcurrent or a short-circuit condition, limiting subsequent disturbances. After the fault condition is removed, the device cools and the internal resistance drops to nearly its initial value, permitting normal equipment operation to resume.
• Indicating - Indicating fuses have visual indication and / or alarm activation. Used for telecommunication, computer and control circuit applications.

Mounting Options

• Solderable or surface mount
• Solderable with leads
• Replaceable with holder or clips

Construction Materials

• Glass

• Ceramic

• Sand 

Standards

A-A-55471 - Fuse, plug, (type tl), time delay, edison base.

A-A-59688 - Fuse, cartridge, instrument type, 5 mm x 20 mm, general requirements for.

References

Image Credits:

SOC America, Inc.