Full Description

This part of IEC 61558 deals with the safety of transformers for construction sites and power supply units incorporating transformers for construction sites. 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 transformers for construction sites and power supply units incorporating transformers for construction sites.

This document is applicable to stationary or portable, single-phase or polyphase, air-cooled (natural or forced) independent or associated transformers, being isolating or safety isolating dry-type transformers for the use on construction sites. 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 takes precedence.

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:
– 25 kVA for single-phase transformers;
– 40 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.

Isolating transformers for construction sites have a no-load output voltage and a rated output voltage exceeding 50 V AC and not exceeding 250 V AC.

Safety isolating transformers for construction sites have a no-load output voltage and a rated output voltage not exceeding 50 V AC.

NOTE 3 This document is applicable to transformers for the supply of electricity in locations as specified in IEC 60364-7-704. The latter also specifies the protection by using an earthed midpoint or starpoint of the output winding.

NOTE 4 Transformers covered by this document are used in applications where it is required by the installation rules or by the appliance specification for protection purposes.

When the transformers are incorporated into low voltage switchgear and controlgear assemblies for construction sites as specified in IEC 61439-4, the additional requirements of IEC 61439-4 apply to the assembly.

NOTE 5 For transformers filled with liquid dielectric or pulverised material, such as sand, additional requirements are under consideration.

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.

It is possible that the future technological development of transformers will require an increase in 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.