Passive filter units for electromagnetic interference suppression — Part 3: Passive filter units for which safety tests are appropriate

Safety Test Procedures and Requirements

Chapter 6 of the standard specifies the safety test plan, and Chapter 7 details the test and measurement procedures:

6.1 Structurally Similar Filters

Defines the criteria for structurally similar filters, including elements such as the same basic design, materials, production processes, and ratings.

6.2 Safety Approval Procedure

Includes sampling requirements and testing procedures, emphasizing the rigorous requirements for safety testing.

Key safety test items

The standard specifies a number of mandatory safety tests, including:

• Insulation resistance test (7.7)
• Withstand voltage test (7.8)
• Leakage current test (7.18)
• Protective conductor resistance test (7.19)
• Impulse voltage test (7.20)
• Endurance test (7.21)
• Passive flammability test (7.22)

Measurement conditions and environmental test requirements

Section 7.1 of the standard specifies the measurement conditions in detail, including standard atmospheric conditions, recovery conditions, arbitration conditions and reference conditions:

Important technical changes and updates

The main technical changes of the 2024 version compared to the 2015 version include:

1. Separation of safety test and performance test clauses: Clarified the independence and mandatory nature of safety test
2. Replacement conditions for X and Y class capacitors: Characteristics and conditions are described separately in Article 4.1
3. Allowing voltage measurement and inductance measurement: Added voltage measurement method in Article 7.3
4. Marking requirements based on residual energy after disconnection: Added relevant marking requirements
5. Changes in sample submission requirements: Group 1A samples now need to be submitted without potting

Test equipment and measuring instrument requirements

The key test equipment involved in the standard includes: High-voltage testers, insulation resistance testers, LCR meters, temperature cycle test chambers, and withstand voltage test equipment are among the equipment required. These devices must comply with the requirements of relevant IEC standards and be calibrated regularly.

Implementation Recommendations and Compliance Strategies

Design Phase Considerations

When designing EMI filters, safety requirements should be prioritized: selecting appropriate X and Y capacitor types, ensuring sufficient creepage and clearance distances, and using compliant insulation materials.

Test Verification Strategies

A phased testing strategy is recommended: perform safety testing first, ensuring compliance with essential safety requirements, and then proceed to performance testing. For filter families with similar structures, the simplified test procedures specified in the standard can be utilized.

Documentation and Marking Requirements

The detailed specifications must include outline drawings and necessary information such as dimensions, installation information, ratings, and characteristics. The filter's markings should include key information such as rated voltage, rated current, temperature range, and manufacturer's logo.

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Actual Case Study of Standard Application

Taking industrial power filters as an example, the key practices of applying the IEC 60939-3 standard include: selecting Class X2 capacitors for line-to-line filtering and Class Y1 capacitors for line-to-ground filtering; ensuring that the reinforced insulation between the primary and secondary sides meets the standard requirements; and conducting a complete safety test sequence, including withstand voltage testing, insulation resistance testing, and leakage current testing.

By following the requirements of this standard, manufacturers can ensure that their filter products not only meet electromagnetic compatibility requirements, but more importantly, guarantee the electrical safety performance of the final product, providing users with reliable safety protection.