Overview
IEC 63522-18:2025 is an international standard published by the International Electrotechnical Commission (IEC) focusing on electrical relays-specifically the tests and measurements related to the thermal resistance of the coil. This standard provides a systematic method to determine the thermal resistance of relay coils, ensuring that devices under test (DUTs) perform reliably under transportation, storage, and operational conditions. Thermal resistance is critical for understanding heat dissipation and thermal behavior in relay coils, directly impacting the device’s performance and longevity.
The standard applies established procedures to measure temperature rise in relay coils when energized at different operating points, enabling manufacturers and engineers to evaluate whether the thermal characteristics comply with specified limits.
Key Topics
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Scope and Purpose: IEC 63522-18:2025 defines the test procedures to evaluate the thermal resistance of relay coils by measuring the temperature rise after thermal equilibrium is reached. It ensures the coil temperature remains within defined limits, thus validating the relay’s robustness in typical operational environments.
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Test Procedure:
- Relays are mounted and energized at four approximately equal points in their operational range.
- Temperature rise (Δt) is measured at each point after thermal equilibrium.
- Measurements occur under controlled ambient conditions, with protection against draughts and radiation.
- The temperature rise formula considers resistance values at ambient and equilibrium temperatures, factoring in the temperature coefficient of resistivity, primarily for copper coils.
- Thermal resistance (R_th) is derived as the temperature rise divided by the coil power at equilibrium.
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Conditions Specification: Set by the user or manufacturer, including:
- Relay mounting configuration
- Connection wire dimensions
- Energization points distribution
- Material temperature coefficients (if not copper)
- Evaluation methods and thermal resistance limits
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Evaluation and Reporting:
- The thermal resistance value provides critical input for design considerations involving heat management in control systems.
- Test reports must detail the DUT description, measurement conditions, resistance values, temperature conditions, and final thermal resistance results to ensure reproducibility and traceability.
Applications
IEC 63522-18:2025 is essential for manufacturers and quality assurance engineers engaged in the design, testing, and certification of electrical relays used across various industries. Its key applications include:
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Relay Design Optimization: Engineers use these tests to assess thermal performance, enabling improvements that prevent overheating and extend relay lifespan.
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Quality Control: Provides a standardized testing framework to confirm that production relays meet thermal performance specifications before deployment.
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Reliability Testing: Ensures relays operate safely under expected environmental and electrical loads, reducing failure risks during transportation, storage, or field use.
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Compliance and Certification: Supports adherence to international standards and regulatory requirements by providing validated data on coil thermal resistance.
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Thermal Management in Electrical Control Systems: Helps system designers assess heat dissipation of relay coils and integrate effective cooling or insulation solutions in control panels and PCBs.
Related Standards
IEC 63522-18:2025 should be used in conjunction with other parts of the IEC 63522 series for comprehensive relay testing and measurement, including:
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IEC 63522-0 (under preparation): General testing and guidance for electrical relays, providing foundational principles and terminology.
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IEC 63522-10 (under preparation): Heating tests for electrical relays, complementing thermal resistance measurements by evaluating heat generation.
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IEC 60050-444:2002: International Electrotechnical Vocabulary (IEV) definitions related to elementary relays, critical for standardized terminology.
Utilizing these related standards ensures comprehensive evaluation of relay functionality and thermal characteristics consistent with international best practices.
Keywords: IEC 63522-18:2025, electrical relays, thermal resistance, relay coil, thermal testing, temperature rise measurement, relay reliability, IEC standards, relay design, electrical testing, coil thermal performance, temperature coefficient, relay thermal evaluation.
Open preview (PDF)Electrical relays – Tests and measurements – Part 18: Thermal resistance of the coil
