BS EN 61558-2-23:2010

Replacement:

This part of IEC61558 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 standard.

NOTE1 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 part 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 may be encapsulated or non-encapsulated.

The rated supply voltage does not exceed 1000V a.c., and the rated supply frequency and the internal operating frequencies do not exceed 500Hz.

This standard used in combination with Part2-16 for Switch mode power supply units (SMPS) is also applicable to power supplies with internal operating frequencies higher than 500Hz. Where the two requirements are in conflict the most severe take precedence

The rated output does not exceed:

• 25kVA for single-phase transformers;

• 40kVA for poly-phase transformers.

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

NOTE2 Transformers intended to supply distribution networks are not included in the scope.

Isolating transformers and power supply units incorporating isolating transformers for construction sites have a no-load output voltage and a rated output voltage exceeding 50V a.c. and not exceeding 250V a.c.

Safety isolating transformers and power supply units incorporating safety isolating transformers for construction sites have a no-load output voltage and a rated output voltage not exceeding 50V a.c.

NOTE3 This standard is applicable to transformers for the supply of electricity in locations as specified in IEC60364-7-704. The latter also specifies the protection by using an earthed midpoint or starpoint of the output winding.

Transformers and power supply units covered by this part are used in applications where it is required by the installation rules or by the appliance specification for protection purposes.

When the transformers or power supply units are incorporated into low voltage switchgear and controlgear assemblies for construction sites as specified in IEC60439-4, the additional requirements of IEC60439-4 will apply to the assembly.

NOTE4 For transformers filled with liquid dielectric or pulverised material, such as sand, additional requirements are under consideration.

NOTE5 Attention is drawn to the following:

• measures to protect the enclosure and the components inside the enclosure against external influences like fungus, vermin, termites, solar-radiation and icing should also be considered;

• the different conditions for transportation, storage, and operation of the transformers and power supply units should also be considered;

• additional requirements in accordance with other appropriate standards and national rules may be applicable to transformers and power supply units intended for use in special environments such as tropical environment.

NOTE6 Future technological development of transformers may necessitate a need to increase the upper limit of the frequencies, until then this standard may be used as a guidance document.