This part of IEC 61558 deals with the safety of auto-transformers for general applications and power supply units incorporating auto-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 auto-transformers for general applications and power supply units incorporating auto-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 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 core power does not exceed:
• 2 kVA for single-phase transformers;
• 10 kVA for polyphase transformers.
The rated output does not exceed:
• 40 kVA for single-phase transformers;
• 200 kVA for polyphase transformers.
This document is applicable to transformers without limitations of the core power and the rated output both being subject to an agreement between the purchaser and the manufacturer.

Where applicable, 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 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 2 Transformers covered by this document are used only in applications where no insulation between circuits is required by the installation rules or by the end product standard.

Attention is drawn to the following, if necessary:
• 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 can be applicable to transformers intended for use in special environments.

Future technological development of transformers can necessitate a need to increase the upper limit of the frequencies. Until then this document can 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 lSO/lEC Guide 51.

One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications and/or group safety publications in the preparation of its publications.