IEC 61558-2-20:2022

Overview

IEC 61558-2-20:2022 - Safety of transformers, reactors, power supply units and combinations thereof - Part 2-20: Particular requirements and tests for small reactors - is the third edition (2022) of this IEC standard. It updates and replaces the 2010 edition and is a technical revision aligned with IEC 61558-1:2017. The standard is a group safety publication under IEC Guide 104 and covers stationary or portable, single‑phase or polyphase, dry‑type small reactors (encapsulated or non‑encapsulated), including those incorporating electronic circuits.

Key application limits given in the standard:

• Rated supply voltage ≤ 1 000 V AC or 1 500 V ripple‑free DC
• Rated/internal operating frequency ≤ 1 100 MHz
• Rated power ≤ 25 kVAR (single‑phase) or 50 kVAR (poly‑phase)
• Additional provisions for reactors with fundamental frequencies > 500 Hz (Annex BB)

Key topics and requirements

IEC 61558-2-20 defines particular safety and test requirements that supplement IEC 61558-1:2017. Major technical topics include:

• General requirements and classification for small reactors
• Marking and user information (nameplate, symbols)
• Protection against electric shock and earthing provisions
• Electrical performance tests: voltage drop, no‑load output voltage, short‑circuit voltage
• Thermal and heating tests and overload/short‑circuit protection
• Insulation and dielectric tests: insulation resistance, dielectric strength, leakage current
• Partial discharge testing (new Annex CC) for assessing insulation integrity
• Mechanical strength and resistance to ingress (dust, moisture)
• Construction, internal wiring, terminals, screws and connections
• Creepage, clearance, resistance to heat/fire/tracking
• Annex AA: characteristic parameter measurement references
• Annex BB: specific requirements for associated reactors operating above 500 Hz

Practical applications and who uses this standard

This standard is used by:

• Design engineers and manufacturers of small dry‑type reactors and inductive components to ensure safe design and compliance.
• Test laboratories and certification bodies performing type and routine safety testing.
• Safety and compliance managers, procurement teams, and OEMs integrating reactors into equipment or power supplies.
• Regulatory authorities and installers who reference safety requirements for installations and equipment approvals.

Adopting IEC 61558-2-20 helps reduce electrical and fire risks, ensures consistent testing practices (including partial discharge and high‑frequency considerations), and aligns product documentation and markings with international safety norms.

Related standards

• IEC 61558-1:2017 (general requirements for transformers, reactors, PSUs) - this part supplements/modifies it.
• Other referenced IEC documents for high‑voltage, ballast, or EMI components (see normative references in the standard).

Keywords: IEC 61558-2-20, small reactors, safety standard, dry‑type reactor, partial discharge, high‑frequency reactors, IEC 61558-1, reactor testing, transformer safety.