IEC 61857-22:2008

Overview

IEC 61857-22:2008 is an international standard developed by the International Electrotechnical Commission (IEC) for the thermal evaluation of wire-wound electrical insulation systems (EIS) using an encapsulated-coil model (ECM). This standard outlines specific requirements for testing and comparing the thermal durability of electrical insulation systems, especially when the final application of the system is unknown. It ensures a harmonized approach for manufacturers and testing bodies to evaluate and qualify encapsulated wire-wound insulation systems consistently.

This second edition of IEC 61857-22 aligns editorially with Parts 1 and 21 of the IEC 61857 series, bringing it up to date with the most recent methodology and terminology.

Key Topics

• Encapsulated-Coil Model (ECM): IEC 61857-22 defines the ECM as a general-purpose test object for evaluating wire-wound electrical insulation systems. The model is constructed using a bobbin, winding wire, wire connectors, and an encapsulant to simulate typical manufacturing and operational stresses.

• Thermal Evaluation Procedures: The standard describes a sequence of tests to assess the thermal endurance of EIS, including:

  • Initial screening (visual inspection, dielectric, mechanical, thermal shock, and moisture exposure tests)
  • Repeated thermal ageing cycles
  • Application of mechanical, thermal, and environmental stresses
  • Dielectric diagnostic assessments after each cycle
  • Defined criteria for end-of-life determination

• Comparison of Reference and Candidate Systems: Tests compare a known (reference) EIS with a new (candidate) EIS, requiring physical similarity, especially in wire size and assembly, to ensure valid results.

• Reporting and Classification: Results are analyzed, reported, and classified per requirements from IEC 61857-1, ensuring consistent reporting for industry benchmarking and regulatory compliance.

Applications

IEC 61857-22:2008 is crucial for:

• Manufacturers of Electrical Equipment: Enables reliable qualification and comparison of wire-wound insulation systems, helping expedite product development and ensure safety before market release.
• Testing Laboratories: Provides standardized procedures for conducting and certifying performance tests on EIS products.
• Quality Assurance: Ensures that insulation systems perform reliably under thermal stress, reducing the risk of field failures in various electrical equipment.
• Certification and Compliance: Used as a benchmark for third-party certification of insulation systems in motors, transformers, and other wire-wound devices where encapsulation is used but final applications are not predetermined.

The standard is applicable to any unknown end-use product using encapsulated wire-wound insulation systems, thus supporting broad industry needs, including innovation and custom solutions.

Related Standards

• IEC 61857-1: General requirements for procedures in thermal evaluation of EIS (particularly for low-voltage systems).
• IEC 61857-21: Procedures specific to other wire-wound models or parameters.
• IEC 60050-195: International Electrotechnical Vocabulary - covers key terminology related to earthing and protection against electric shock.

Conclusion

IEC 61857-22:2008 provides a globally recognized procedure for the thermal evaluation of encapsulated wire-wound electrical insulation systems. Its adoption helps manufacturers and laboratories ensure product reliability, regulatory compliance, and consistent performance across a diverse range of electrical equipment. Aligning with this IEC standard strengthens product safety, fosters international market acceptance, and supports innovation in electrical insulation technology.