Resettable Fuse (PTC): Max Voltage 6V to 600V

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

Parameter	Typical range	Notes & selection driver
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

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

IEC 60730, UL 1434, IEC 60950-1

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

Typical Suppliers & Equivalents

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

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

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Inspection readiness

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Supplier transparency

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Manufacturers of Resettable Fuse (PTC)

Manufacturer profiles associated with Resettable Fuse (PTC).

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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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.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Resettable Fuse (PTC)