BS EN IEC 61558-2-1:2025

Safety of transformers, reactors, power supply units and combinations thereof. Particular requirements and tests for separating transformers and power supply units incorporating separating transformers for general applications | Status: Current

1 Scope Replacement This part of IEC 61558 deals with the safety of separating transformers for general applications and power supply units incorporating separating transformers for general applications. Transformers incorporating electronic circuits are also covered by this document.

NOTE 1 Safety includes electrical, thermal and mechanical aspects.

Unless otherwise specified, from here onward, the term transformer covers separating transformers for general applications and power supply units incorporating separating transformers for general applications. For power supply units (linear), this document is applicable. For switch mode power supply units, IEC 61558‑2‑16 is applicable. This document does not apply to transformers covered by IEC 60076‑11. This document is applicable to stationary or portable, single-phase or polyphase, air-cooled (natural or forced) independent or associated dry- type transformers. The windings can be encapsulated or non-encapsulated. The rated supply voltage does not exceed 1 000 V AC and the rated supply frequency and the internal operating frequencies do not exceed 500 Hz. The rated output does not exceed:

• – 1 kVA for single-phase transformers,
• – 5 kVA for polyphase transformers;

This document is applicable to transformers without limitation of the rated output, subject to an agreement between the purchaser and the manufacturer.

NOTE 2 Transformers intended to supply distribution networks are not included in the scope.

The no-load output voltage or the rated output voltage does not exceed 1 000 V AC or 1 415 V ripple-free DC. For independent transformers the no-load output voltage and / or the rated output voltage is not less than 50 V AC or 120 V ripple-free DC. This document is not applicable to external circuits and their components intended to be connected to the input terminals and output terminals of the transformers.

NOTE 3 Transformers covered by this document are only used in applications where double or reinforced insulation between circuits is not required by the installation rules or by the end product standard.

NOTE 4 Normally the separating transformers are intended to be used with equipment to provide voltages different from the supply voltage for the functional requirements of the equipment. The protection against electric shock may be provided or completed by other features of the equipment, such as the body. Parts of output circuits may be connected to the input circuits or to protective earthing.

Attention is drawn to the following:

• – for transformers intended to be used in vehicles, on board ships, and aircraft, additional requirements (from other applicable standards, national rules, etc.);
• – measures to protect the enclosure and the components inside the enclosure against external influences such as fungus, vermin, termites, solar-radiation, and icing;
• – the different conditions for transportation, storage, and operation of the transformers;
• – additional requirements in accordance with other appropriate standards and national rules may be applicable to transformers intended for use in special environments.

Future technological development of transformers may necessitate a need to increase the upper limit of the frequencies. Until then this document may be used as a guidance document. This group safety publication focusing on safety guidance is primarily intended to be used as a product safety standard for the products mentioned in the scope, but is also intended to be used by technical committees in the preparation of publications for products similar to those mentioned in the scope of this group safety publication, in accordance with the principles laid down in IEC Guide 104 and ISO/IEC Guide 51. One of the responsibilities of a technical committee is, wherever applicable, to make use of BSPs and/or GSPs in the preparation of its publications.