IEC 61558-2-12:2024

Overview

IEC 61558-2-12:2024 is the third edition of the IEC safety standard for constant voltage transformers and power supply units for constant voltage. It specifies particular safety requirements and tests for stationary or portable, single‑phase or polyphase, dry‑type (air‑cooled) constant voltage auto‑, separating, isolating and safety‑isolating transformers and linear power supply units. This edition aligns structure and references with IEC 61558-1:2017, moves construction descriptions to that part, and introduces a new symbol for linearly regulated output voltage. The standard is a group safety publication under IEC Guide 104.

Key Topics

The standard supplements IEC 61558-1 and covers practical technical requirements and tests including:

• Ratings, classification and marking (rating limits, supply voltage/frequency, symbols)
• Protection against electric shock and SELV considerations
• Output performance: output voltage/current under load, no‑load voltage, short‑circuit voltage
• Thermal and electrical tests: heating, insulation resistance, dielectric strength, leakage current
• Short‑circuit and overload protection and routine production tests (Annex L)
• Mechanical and environmental tests: mechanical strength, protection against ingress of dust/moisture, resistance to heat/fire/tracking and rusting
• Construction and components: internal wiring, terminals, earthing provisions, screws/connections, creepage and clearance distances
• Applicability limits included in the standard: rated supply voltage up to 1000 V AC, supply frequency up to 500 Hz, internal resonant frequency up to 30 kHz and internal operating frequency up to 100 MHz. Rated output examples cited in the standard include values such as 40 kVA (single‑phase auto), 200 kVA (polyphase auto), 25 kVA (single‑phase separating/isolating), etc.

Applications

Who uses IEC 61558-2-12:2024 and why:

• Transformer and linear power supply manufacturers - to design, test and certify products that meet international safety requirements.
• Test laboratories and certification bodies - to conduct required safety and routine tests and assess conformity.
• Design and safety engineers - to ensure installations and equipment meet protection, thermal and insulation criteria.
• Procurement and compliance teams - to specify safe transformers/power supplies for industrial, control and equipment applications.
• It is also referenced when combining linear supplies with SMPS designs; where switching supplies are involved IEC 61558-2-16 is used together with this document and the more stringent requirement prevails.

Related Standards

• IEC 61558-1:2017 (general requirements)
• IEC 61558-2-16 (switch‑mode power supply particular requirements)
• IEC Guide 104 (group safety publications)
• Other related IEC documents referenced for protection and electrical installation practices (e.g. IEC 61140, IEC 60364 series, IEC 60204-1)

Keywords: IEC 61558-2-12:2024, constant voltage transformers, power supply units, safety requirements, tests, IEC 61558 series, linearly regulated output.