Fuses

1. Definition

1.1 Fuse

A fuse is a protective component designed to disconnect a circuit when the electrical current exceeds a safe limit.
It contains a thin conductor that melts when overheated, stopping the flow of electricity and protecting components from damage.

Fuse examples

Fuse Symbol

Fuse symbol

1.2 Types of Fuses

  • Glass Cartridge Fuse : transparent tube, common in electronics.
  • Blade Fuse (Automotive) : plastic body with metal blades, used in vehicles.
  • Resettable Polyfuse (PTC) : automatically recovers after the fault is removed.

2. Features

  • Current rating : maximum current before fuse blows (e.g., 1A, 10A).
  • Voltage rating : maximum circuit voltage it can safely interrupt.
  • Blow characteristics :
    • Fast-blow: trips quickly for sensitive electronics.
    • Slow-blow: tolerates short surges, used with motors or power supplies.
  • Reset type : single-use (replaceable) or resettable.

4. How to Use

Safety Note

Always replace a blown fuse with one that has the same current and voltage rating. Using a higher-rated fuse can cause overheating and fire hazards.

4.1 Identify Fuse Rating

  • Ratings are usually printed on the fuse body or metal caps.
  • Example: “250V 5A” means it will blow at currents above 5A at up to 250V.

Fuse rating

4.2 Installing a Fuse

  • Place in series with the circuit or device being protected.
  • Ensure proper mechanical mounting (fuse holder or PCB mount).
  • For automotive fuses, insert into the correct slot in the fuse box.

4.3 Applications

  • Circuit protection in electronics.
  • Automotive wiring systems.
  • AC/DC power supplies.
  • Industrial control systems.

Video Explanation

video coming soon