Resettable Fuses

Resettable fuses, also known as self-resetting fuses, are a reusable type of circuit protection device used across a wide range of applications. Like regular fuses, these fuses trip when the current becomes too high.

However, unlike traditional fuses that need replacing after a fault, an automatic resettable fuse will function again once the fault is cleared and conditions return to an acceptable level.

How Do Resettable Fuses Work?

Resettable fuses function on a Positive Temperature Coefficient (PTC) principle. When a fault like overcurrent causes a temperature increase, the PTC fuse's core rapidly heats up and expands, which increases its resistance. This surge in resistance effectively reduces the current to a safe level, protecting the circuit.

Once the fault is corrected and the core cools, it contracts, causing the resistance to decrease. In turn, the circuit is reset, enabling current to flow normally again.

Types of Resettable Fuses

By Technology

• Polymeric Positive Temperature Coefficient (PPTC) Fuses: The most common type, these fuses use a polymer that increases resistance when heated by an overcurrent, protecting circuits.
• Polymer Electrothermal Devices (PEDs): Similar to PPTC fuses but with faster response times and higher current-handling capabilities, PEDs are suited for high-performance applications where quick overcurrent protection is crucial.
• Resettable Thermal Cutoffs (RTCs): These rely on a bimetallic strip that bends to open a circuit when exposed to excessive heat. They automatically reset once the temperature normalises.
• Resettable Electronic Fuses: Utilising electronic components like transistors or integrated circuits, these fuses provide precise monitoring and protection. They can be reset electronically, eliminating the need for manual intervention.
• Resettable Solid-State Fuses: Incorporating semiconductor materials that change their electrical properties in response to temperature or current changes, these fuses offer fast response times and high reliability for demanding applications.

By Mounting Method

• SMD (Surface Mount) Resettable Fuses: These PCB resettable fuse devices are soldered directly onto a PCB (printed circuit board). When an overcurrent is detected, they trip and break the circuit, then automatically reset when conditions are safe.
• Wire-Ended Resettable Fuses: These fuses feature wire leads for through-hole mounting or direct connection. They are widely used in automotive, security systems, and telecommunications, offering a maintenance-free, self-resetting function for protecting against excessive currents. Leaded PCB mount varieties are also available.

How to Install Resettable Fuses

Installing a resettable fuse is a straightforward process. Follow these steps for a safe and successful installation:

1. Select the correct fuse: Begin by selecting a resettable fuse that matches the voltage and current requirements of your circuit for optimal protection.
2. Power down the circuit: For safety, always disconnect the power to the circuit before attempting any installation. This helps to prevent electric shock and damage to components.
3. Install the fuse: Install the fuse based on the mounting method. For example, you may need to solder a surface mount resettable fuse or secure the ends of a wire-ended fuse.
4. Verify connections: Ensure all connections are secure and properly insulated.
5. Test the circuit: Restore power and test the circuit. The automatic resettable fuse should allow normal current flow but trip on a fault.

Applications of Resettable Fuses

Resettable fuses are often used in circuits where an automatic reset after a fault is desirable. They’re essential across a wide range of industries and sectors:

Consumer Electronics

Resettable fuses protect sensitive components in consumer devices like USB ports and battery packs. For instance, PCB resettable fuses are commonly used to prevent damage from overcurrents caused by faulty external devices.

Smart Home Devices

In smart home devices, an SMD resettable fuse protects integrated circuits and sensitive components from overcurrents. It is a compact and reliable solution for home automation hubs and connected appliances.

Security Systems

A self-resetting fuse protects alarm panels and sensors from power surges, ensuring continuous operation without manual intervention, which is critical for security.

Industrial Control Systems

In industrial control systems, a PTC fuse safeguards motors and actuators from overcurrent conditions. Its self-resetting function minimises downtime on production lines, enhancing operational efficiency.

Automotive Electronics

Car fuses, such as 12V resettable fuses, protect vehicle wiring and components, including car stereos and lighting, from short circuits and overcurrents. This safeguards crucial systems from electrical faults.

Telecommunications Infrastructure

Sensitive network equipment and communication lines rely on resettable fuses for protection against power surges. This ensures reliable connectivity.

Medical Devices

Resettable electronic fuses are used in medical devices to ensure patient safety. They provide highly reliable protection for equipment like monitors and diagnostic tools, safeguarding against unexpected current surges.

How to Choose the Right Reusable Fuse

When selecting a reusable fuse, there are several key factors to consider to ensure optimal performance and safety.

• Current Rating: Choose a fuse with a current rating that matches or slightly exceeds your circuit's operational current. By doing so, you can avoid false tripping.
• Voltage Rating: The fuse's voltage rating must be equal to or higher than the maximum voltage in your circuit for safe and reliable operation.
• Mounting Method: Select a fuse that is compatible with your installation method, such as surface-mounting or through-hole mounting.
• Response Time: Different fuses have varying response times. Choose a fuse that provides protection fast enough for your application's specific overcurrent conditions.
• Operating Temperature: Ensure the fuse's operating temperature range is suitable for your application's environment to prevent false tripping or fuse failure.

Buy Resettable Fuses from RS Australia

RS Australia is a trusted supplier and distributor of resettable fuses, including DC and 2 amp options, providing a comprehensive selection of these circuit protection devices. Our products are sourced from reputable brands, such as Bourns, Littelfuse, Wickmann, and Eaton, ensuring high-quality options for every application.

Beyond resettable fuses, we also offer a wide array of other circuit protection components, including porcelain fuses, mini breakers, and thermal breakers, to meet all your electrical safety needs.

Explore the full range of products on our user-friendly online site and have your desired items shipped directly to your door. With our flexible delivery options, we ensure that you receive your products at your convenience.

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