IEC 61558-2-12 Ed. 3.0 b:2024 ✓ Most Recent

Replacement:

This part of IEC 61558 deals with the safety of constant voltage transformers for general applications and power supply units for constant voltage for general applications. Constant voltage 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 constant voltage transformers for general applications and power supply units for constant voltage for general applications.

This document is applicable to stationary or portable single-phase or polyphase, air-cooled (natural or forced) independent or associated dry-type:
– constant voltage auto-transformers;
– constant voltage separating transformers;
– constant voltage isolating transformers;
– constant voltage safety isolating transformers.

The windings can be encapsulated or non-encapsulated.

For power supply units (linear) this document is applicable. For switch mode power supply units IEC 61558-2-16 is applicable together with this document. Where two requirements are in conflict, the most severe take precedence.

The rated supply voltage does not exceed 1 000 V AC. The rated supply frequency does not exceed 500 Hz, the internal operating resonant frequency does not exceed 30 kHz and the internal operating frequency does not exceed 100 MHz.

The rated output does not exceed:
– 40 kVA for single-phase constant voltage auto-transformers;
– 200 kVA for polyphase constant voltage auto-transformers;
– 25 kVA for single-phase constant voltage separating transformers and constant voltage isolating transformers;
– 40 kVA for polyphase constant voltage separating transformers and constant voltage isolating transformers;
– 10 kVA for single-phase constant voltage safety isolating transformers;
– 16 kVA for polyphase constant voltage safety isolating 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.

Where applicable to constant voltage auto-transformers
– the no-load output voltage or the rated output voltage does not exceed 1 000 V AC or 1 415 V ripple-free DC, and for independent constant voltage auto-transformers the no-load output voltage and the rated output voltage exceed 50 V AC or 120 V ripple-free DC;
– constant voltage auto-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.

Where applicable to constant voltage separating transformers
– the no-load output voltage or the rated output voltage does not exceed 1 000 V AC or 1 415 V ripple-free DC, and for independent constant voltage separating transformers the no-load output voltage and the rated output voltage exceed 50 V AC or 120 V ripple-free DC;
– constant voltage separating transformers covered by this document are used only in applications where double or reinforced insulation between circuits is not required by the installation rules or by the end product standard.

Where applicable to constant voltage isolating transformers
– the no-load output voltage or the rated output voltage does exceed 50 V AC or 120 V
ripple-free DC and where applicable, does not exceed 500 V AC or 708 V ripple-free DC.
The no-load output voltage and the rated output voltage can be up to 1 000 V AC or 1 415 V ripple-free DC for special applications;
– constant voltage isolating transformers covered by this document are used only in applications where double or reinforced insulation between circuits is required by the installation rules or by the end product standard.

Where applicable to constant voltage safety isolating transformers
– the no-load output voltage or the rated output voltage does not exceed 50 V AC or 120 V ripple-free DC;
– constant voltage safety isolating transformers covered by this document are used only in applications where double or reinforced insulation between circuits is required by the installation rules or by the end product standard.

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.

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 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 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.