Thermal Sensor / Fusible Alloy: Voltage Rating 250V AC/DC

Q: What is the difference between fusible alloy sensors and bimetallic thermal protectors?

Fusible alloy sensors provide one-time irreversible protection by melting at a specific temperature, while bimetallic devices can reset after cooling. Fusible alloys offer more precise temperature triggering and are used where resetting isn't required or could be dangerous.

Q: Can fusible alloy thermal sensors be used in high-vibration environments?

Yes, when properly housed in vibration-resistant casings. The solid alloy remains stable until melting point, but mounting should minimize mechanical stress that could cause premature failure.

Q: Are lead-free fusible alloys available for RoHS compliance?

Yes, modern formulations use bismuth-tin-indium or other lead-free alloys with similar melting characteristics while meeting environmental regulations.

Component Specifications

Definition

A thermal protection component that uses a fusible alloy element designed to melt at a specific temperature threshold, thereby mechanically or electrically disconnecting a circuit to prevent overheating damage in electrical machines and devices.

Working Principle

The fusible alloy is calibrated to melt at a precise temperature (typically between 70°C-150°C). When ambient or component temperature reaches this threshold, the alloy liquefies, triggering a mechanical spring or contact mechanism to open the circuit, interrupting current flow and preventing thermal damage.

Materials

Fusible alloy (typically bismuth-tin-lead-cadmium or lead-free alternatives like bismuth-tin-indium), copper terminals, ceramic or polymer housing, spring mechanism.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Response Time	<5 seconds at threshold
Terminal Type	Quick-connect or screw terminals
Current Rating	1A-30A
Voltage Rating	250V AC/DC
Housing Material	UL94 V-0 rated polymer or ceramic
Melting Temperature	72°C-150°C (customizable)
Operating Temperature Range	-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

ISO 8820, DIN 72581-3, UL 248, IEC 60269

Parent Products

This component is used in the following industrial products

Thermal Disconnector

A safety component within a Surge Protection Device (SPD) that automatically disconnects the circuit when excessive heat is detected, preventing fire hazards.

View Product Details

Engineering Analysis

Risks & Mitigation

Single-use (non-resettable)
Environmental temperature affects calibration
Mechanical damage can cause false triggering
Alloy degradation over time at high temperatures

FMEA Triads

Trigger: Alloy contamination during manufacturing
Failure: Inconsistent melting temperature
Mitigation: Strict material purity controls and batch testing

Trigger: Vibration-induced mechanical stress
Failure: Premature fracture or disconnection
Mitigation: Shock-absorbing mounting and strain relief design

Trigger: Oxidation of alloy surface
Failure: Increased melting temperature over time
Mitigation: Protective coatings and hermetic sealing

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±3°C melting temperature tolerance, ±10% current rating tolerance

Test Method

Temperature ramp testing in controlled oven with current load simulation, vibration testing per IEC 60068-2-6, dielectric strength testing at 2x rated voltage

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

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Thermal Sensor / Fusible Alloy

Manufacturer profiles associated with Thermal Sensor / Fusible Alloy.

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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 fusible alloy sensors and bimetallic thermal protectors?