IEC 61558-2-2:2007

Overview

IEC 61558-2-2:2007 specifies safety requirements and testing methods for control transformers and power supplies incorporating control transformers, as well as similar products. Developed by the International Electrotechnical Commission (IEC), this standard addresses the essential aspects of electrical, thermal, and mechanical safety, ensuring that these components are suitable for their intended applications. This edition updates and revises the previous version, aligning it with the latest Part 1 and expanding the scope to include power supplies. As a group safety publication, IEC 61558-2-2:2007 provides crucial guidelines for manufacturers, installers, and end-users in achieving compliance with international standards.

Key Topics

• Scope of Application: The standard covers stationary or portable, single-phase or poly-phase, air-cooled (naturally or forced) control transformers and power supplies, with rated supply voltage not exceeding 1,000 V AC and frequency not exceeding 500 Hz.
• Safety Aspects: Addresses electrical safety (including protection against electric shock), thermal safety (heating and overload protection), and mechanical safety (resistance to impact and environmental conditions).
• Testing Methods: Specifies particular test procedures for control transformers and power supplies, including tests for dielectric strength, insulation resistance, mechanical robustness, and protection against ingress of dust, moisture, or foreign objects.
• Marking and Information: Requirements for product labeling, terminal identification, and provision of safety information to ensure correct installation and maintenance.
• Construction Requirements: Establishes criteria for materials, internal wiring, terminals, earthing provisions, and robustness against environmental influences such as heat, fire, or rusting.

Applications

Control transformers and power supplies incorporating control transformers are widely used in industrial, commercial, and utility settings. Key applications include:

• Automation and Control Systems: Supplying power to control circuits for industrial machines, processing equipment, and automated systems, where voltage needs to be different from the supply for functional or safety reasons.
• Signaling and Interlocking: Providing safe and reliable power to signaling devices, interlocks, and safety circuits in electrical panels and machinery.
• Panel Building and Switchgear: Used in electrical panels for distributing safe, isolated voltages to relays, contactors, and other devices.
• Machinery and OEM Equipment: Integral in the design and operation of factory machinery, production lines, and custom-built equipment.
• Adaptation to Special Environments: Installed in environments with specific needs, such as vehicles, ships, or areas exposed to tropical conditions, where additional protection against external factors may be required.
• Power Quality and Safety Enhancement: Helps to reduce risk of electric shock and ensures compliance with international safety mandates.

Related Standards

• IEC 61558-1: General requirements for safety of power transformers, power supplies, reactors, and similar products. Part 2-2 supplements and modifies this base standard.
• IEC 60076-11: Dry-type power transformers - referenced for transformer types not covered by IEC 61558-2-2.
• IEC Guide 104: Preparation and use of group and basic safety publications for electrotechnical products.
• Other IEC 61558 Parts: Cover additional types of transformers and clarify further particular requirements for specialized use cases.

Practical Value

Complying with IEC 61558-2-2:2007 ensures that manufacturers and users meet internationally recognized safety standards for control transformers and related power supplies. This supports market access, reliability, and protection for personnel and equipment. Using this standard helps organizations avoid safety hazards, supports regulatory compliance, and aligns product designs with current industry best practices in transformer safety.

Keywords: IEC 61558-2-2, safety standard, control transformers, power supplies, electrical safety, thermal protection, mechanical safety, transformer testing, group safety publication, IEC standards.