Electrical Fuse

A fuse is used for protecting electrical devices and components from over currents and short circuits. A fuse works by interrupting the flow of current through the melting of an internal element.

General specifications
Listed below are common specifications that apply to electric fuses are:

• Material of construction: These include:
  • Ceramic
  • Sand
  • Glass
  
  
• Fuse types: These include:
  • Miniature: These fuses are available in dimensions of 5x20mm and 6.3x32mm.
    
    
  • Subminiature or micro: Also known as micro fuses, these have very small dimensions (no principal dimension greater than 10 mm) and aresuitable for compact circuit board layouts.
    
    
  • Midget: These refer to fuses that have 13/32" diameter.
    
    
  • Automotive: These fuses are only used in automotive.
    
    
  • Blade type: These fuses are typically used in low voltage, high current applications.
    
    
  • PC board: These fuses are specifically used on PC boards.
    
    
  • Protective: These fuses are used for protecting secondary circuits or low voltage ICs.
    
    
• Mounting: These include:
  • Solderable or surface mount
  • Solderable with leads
  • Replaceable with holder or clips
    
    
• Performance Ratings
  There are certain performance criteria that one must consider while selecting fuses. These are:
  • Voltage rating: It is the maximum voltage, up to which a safe fault current interruption will occur.
    
    
  • Current rating: It is the maximum continuous operating current of the circuit.
    
    
  • Rated breaking capacity: It is the short circuit current at which the fuse can blow without being destructed.
    
    
  • Interrupt rating: These can be high interrupt, medium interrupt, or low interrupt.
    
    
• Performance Characteristics
  There are certain performance characteristics that one must consider while selecting fuses. These are:
  • Fast acting: These fuses are used in circuits that have inrush currents or where the over current must be quickly interrupted.
    
    
  • Time lag: These fuses are used in circuits where high starting inrush currents occur and decay gradually.

Operating temperature of fuse is another environmental parameter that must be considered.