Thermal Fuse: Voltage Rating 250V AC/DC

Component Specifications

Definition

A thermal fuse is a critical safety component designed to protect electrical equipment from overheating by permanently breaking the circuit when a predetermined temperature threshold is reached. Unlike circuit breakers or resettable thermal cutoffs, thermal fuses operate through irreversible physical or chemical changes, typically involving a fusible alloy or pellet that melts at the specified temperature, thereby severing the electrical connection. These devices are essential for preventing fire hazards, equipment damage, and electrical failures in applications where temperature control is vital.

Working Principle

The thermal fuse operates on the principle of thermal expansion and phase change. It contains a fusible element (usually a low-melting-point alloy or organic material) that remains solid under normal operating temperatures. When the ambient temperature exceeds the rated temperature (e.g., 72°C, 94°C, 130°C), the fusible element melts or deforms, causing a spring-loaded mechanism to disconnect the electrical contacts permanently. This irreversible action ensures the circuit remains open even after cooling, requiring replacement of the fuse to restore functionality.

Materials

Housing: Phenolic resin, ceramic, or high-temperature plastic; Fusible element: Eutectic alloys (e.g., tin-bismuth, lead-tin), organic compounds, or low-melting-point metals; Contacts: Copper alloy or silver-plated materials; Insulation: Fiberglass or mica.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Response Time	Less than 5 seconds at 10°C above rated temperature
Current Rating	1A to 15A
Voltage Rating	250V AC/DC
Rated Temperature	72°C to 240°C (common range: 72°C, 94°C, 130°C)
Dielectric Strength	1500V AC for 1 minute
Holding Temperature	Rated temperature ±5°C
Insulation Resistance	>100 MΩ at 500V DC

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

Standards

ISO 8820, DIN 43653, UL 248, IEC 60127

Parent Products

This component is used in the following industrial products

Surge Protection Module

A protective electronic component designed to limit transient voltage spikes in electrical circuits.

View Product Details

Engineering Analysis

Risks & Mitigation

Incorrect temperature rating leading to premature failure or inadequate protection
Poor installation causing thermal lag or inaccurate response
Exposure to moisture or chemicals degrading performance
Using non-compliant fuses violating safety regulations

FMEA Triads

Trigger: Excessive ambient temperature due to blocked ventilation or component failure
Failure: Thermal fuse fails to activate, allowing overheating and potential fire
Mitigation: Regular maintenance of cooling systems, use of fuses with appropriate temperature ratings, and redundancy with temperature sensors

Trigger: Mechanical stress or vibration damaging the fusible element
Failure: False activation or open circuit under normal conditions
Mitigation: Secure mounting with shock-absorbing materials, selecting robust housing designs

Trigger: Corrosion from humidity or contaminants
Failure: Increased resistance or intermittent connections, reducing reliability
Mitigation: Apply conformal coatings, use sealed fuses, and control environmental exposure

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Temperature rating ±5°C, current rating ±10% under standard test conditions

Test Method

Testing per ISO 8820: Thermal cycling, dielectric strength verification, and response time measurement in controlled ovens or environmental chambers

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

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Thermal Fuse

Manufacturer profiles associated with Thermal Fuse.

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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

What is the difference between a thermal fuse and a thermal cutoff?

A thermal fuse is non-resettable and must be replaced after activation, while a thermal cutoff (like a bimetallic strip) can reset automatically after cooling. Thermal fuses provide more reliable protection in critical applications.

How do I select the right thermal fuse for my application?

Choose based on rated temperature (slightly above normal operating temperature), current/voltage ratings, response time, and environmental conditions. Always refer to manufacturer datasheets and safety standards like UL or IEC.

Can a thermal fuse be used in series with other fuses?

Yes, thermal fuses are often used in series with electrical fuses for comprehensive protection—thermal fuses guard against overheating, while electrical fuses protect against overcurrent.

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.

Thermal Fuse