EN IEC 60691:2023/FprA2:2025

Overview

EN IEC 60691:2023/FprA2:2025 is the second amendment to the international standard covering thermal-links, focusing on updated requirements and application guidelines. Thermal-links are crucial safety components designed to provide overcurrent protection in electrical systems by responding to excessive temperature conditions. This amendment, prepared by the CLC and IEC SC 32C committee on miniature fuses, introduces revised testing protocols and clarifications to ensure higher reliability and safety.

Scheduled for stability until 2028, the document reflects the latest best practices in the measurement and verification of thermal protection devices and aligns with relevant international safety standards. It is notably recognized across multiple European languages and countries, with specific annex requirements mandated in Germany.

Key Topics

• Thermal-link Testing Methodology
  The amendment describes updated procedures for measuring and stabilizing test temperatures using static-air ovens. These include:

  • Precise temperature measurement near the test fixture assembly center with fine wire thermocouples to minimize measurement interference.
  • Strict temperature uniformity requirements: ±1 K variation at 200 °C or below, and ±0.5% above 200 °C.
  • Oven temperature stabilization criteria defined by two consecutive temperature readings within 1 K, spaced 5 minutes apart.

• Test Fixture and Load Connection
  The specification ensures that test fixture wiring does not introduce heat sink effects that could alter thermal-link temperature readings. Proper insulation and positioning within the oven are mandated to avoid direct contact with oven walls.

• Duration and Compliance Testing
  Thermal-links are energized under rated current conditions for 24 hours or longer, as declared by the manufacturer, to verify continuous conductivity post-test. The goal is to confirm no unintentional state changes occur, ensuring reliable operation under thermal stress.

• Packaging and Assembly Requirements
  The amendment references specific provisions in Annex H concerning packaged thermal-link assemblies, highlighting the importance of maintaining performance consistency in integrated devices.

Applications

Thermal-links covered by EN IEC 60691:2023/FprA2:2025 are widely used for overcurrent and temperature-overload protection in various electrical and electronic systems, including:

• Industrial electrical equipment
• Consumer appliances
• Heating and ventilation systems
• Miniature fuse assemblies in control panels
• Automotive and transportation electrical systems

The clear test procedures and application guidelines support manufacturers and safety engineers in ensuring compliance with international safety norms while optimizing the reliability of thermal protection components.

Related Standards

This amendment complements and builds upon the base standard IEC 60691 on thermal-links and is associated with:

• IEC SC 32C standards on miniature fuses and their safety requirements
• IEC and CENELEC standards concerning overcurrent protective devices
• Regional safety standards requiring specific annexes, such as German national implementation of Annex I for holding temperature tests
• Other fuse and overcurrent protection standards within the ICS 29.120.50 category

By harmonizing definitions, test methods, and application instructions, this amendment facilitates global standardization and supports manufacturers in meeting both international and regional compliance mandates.

Keywords: EN IEC 60691 amendment 2, thermal-links, thermal protection devices, overcurrent protection, static-air oven testing, miniature fuses, IEC 60691:2023, thermal fuse standards, electrical safety components, fuse testing requirements.