INDUSTRY COMPONENT

Resettable Fuse (PTC)

A resettable fuse (PTC) is a polymer-based positive temperature coefficient device that provides overcurrent protection by increasing resistance when heated, automatically resetting after fault clearance.

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Component Specifications

Definition
A Resettable Fuse, also known as a Polymeric Positive Temperature Coefficient (PPTC) device, is a passive electronic component used for overcurrent protection in electrical circuits. It consists of a conductive polymer composite with embedded conductive particles. Under normal operating conditions, it maintains low resistance. When excessive current flows, Joule heating causes the polymer to expand, separating conductive particles and dramatically increasing resistance (typically by 3-6 orders of magnitude), thereby limiting current flow. After the fault is removed and the device cools, it returns to its low-resistance state, making it reusable without replacement.
Working Principle
Operates on the positive temperature coefficient (PTC) effect of conductive polymers. At normal temperatures, conductive particles within the polymer matrix form continuous conductive paths. When overcurrent occurs, heat generated by I²R heating causes the polymer to thermally expand, breaking these conductive paths and increasing resistance exponentially. This creates a high-impedance state that limits current to a safe trickle level. Once power is removed and the device cools below its trip temperature, the polymer contracts, re-establishing conductive paths and resetting the device to its low-resistance state.
Materials
Conductive polymer composite (typically polyethylene or polyvinylidene fluoride matrix with carbon black or metal particle fillers), nickel-plated copper electrodes, epoxy coating for environmental protection.
Technical Parameters
  • Trip Time Seconds at 2x hold current
  • Resistance 0.01Ω to 10Ω
  • Max Voltage 6V to 600V
  • Hold Current 0.1A to 40A
  • Trip Current Typically 2x hold current
  • Operating Temperature -40°C to 85°C
Standards
IEC 60730, UL 1434, IEC 60950-1

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Resettable Fuse (PTC).

resettable fuse PTC fuse polymeric PTC overcurrent protection circuit protection self-resetting fuse PPTC device line protection Resettable Fuse (PTC) Resettable Fuse (PTC) in Electrical Equipment Manufacturing

Parent Products

This component is used in the following industrial products

Line Protection Circuitry

Electronic circuitry within a transceiver designed to protect signal lines from electrical faults such as overvoltage, overcurrent, and electrostatic discharge (ESD).

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Engineering Analysis

Risks & Mitigation
  • Thermal runaway if improperly rated
  • Increased resistance after multiple trips
  • Slow response time compared to semiconductor devices
  • Voltage derating at high temperatures
FMEA Triads
Trigger: Overcurrent exceeding trip rating
Failure: Device trips to high-resistance state, interrupting circuit operation
Mitigation: Proper current rating selection with 25-50% margin, thermal management to prevent nuisance tripping
Trigger: Mechanical stress or vibration
Failure: Cracking of polymer matrix leading to permanent high resistance
Mitigation: Proper mounting with strain relief, vibration-resistant designs, conformal coating
Trigger: Environmental contamination
Failure: Reduced trip consistency or failure to reset
Mitigation: Sealed packages for harsh environments, regular inspection in contaminated areas

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance
±20% on hold current, ±25% on trip current under standard test conditions
Test Method
IEC 60730-1 Annex H for automatic electrical controls, UL 1434 for thermistor-type devices

Buyer Feedback

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Frequently Asked Questions

How does a resettable PTC fuse differ from traditional fuses?

Traditional fuses operate by melting a metal element permanently, requiring replacement after tripping. PTC fuses use polymer expansion to increase resistance temporarily, automatically resetting when power is removed and the device cools, eliminating replacement needs.

What causes a PTC fuse to trip?

Tripping occurs when current exceeds the hold rating, generating sufficient heat through I²R heating to expand the polymer matrix. Common causes include short circuits, overload conditions, or inrush currents exceeding device specifications.

How long does it take for a PTC fuse to reset?

Reset time varies from seconds to minutes depending on device size, ambient temperature, and mounting conditions. Complete cooling to ambient temperature is required for full reset to low-resistance state.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

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