BS EN 61558-2-12:2011

This standard BS EN 61558-2-12:2011 Safety of transformers, reactors, power supply units and combinations thereof is classified in these ICS categories:

• 29.180 Transformers. Reactors

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 standard.

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 part 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 may be encapsulated or non-encapsulated.

This standard is applicable to transformers and power supply (linear) with internal operating frequencies not exceeding 500 Hz.

This standard used in combination with Part 2-16 for switch mode power supply (SMPS) units is also applicable to power supplies with internal operating frequencies higher than 500 Hz. Where the two requirements are in conflict, the most severe take precedence.

The rated supply voltage does not exceed 1 000 V a.c., 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 poly-phase constant voltage auto-transformers;

• –        25 kVA for single-phase constant voltage separating transformers and constant voltage isolating transformers;

• –        40 kVA for poly-phase constant voltage separating transformers and constant voltage isolating transformers;

• –        10 kVA for single-phase constant voltage safety isolating transformers;

• –        16 kVA for poly-phase constant voltage safety isolating transformers.

This part 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 a.c. or 1 415 V ripple-free d.c., and for independent constant voltage auto-transformers, the no-load output voltage and the rated output voltage exceed 50 V a.c. or 120 V ripple-free d.c.;

• –        constant voltage auto-transformers covered by this part 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 a.c. or 1 415 V ripple-free d.c., and for independent constant voltage separating transformers, the no-load output voltage and the rated output voltage exceed 50V a.c. or 120 V ripple-free d.c.;

• –        constant voltage separating transformers covered by this part 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 a.c. or 120 V ripple-free d.c. and where applicable, does not exceed 500 V a.c. or 708 V ripple-free d.c. The no-load output voltage and the rated output voltage may be up to 1 000 V a.c. or 1 415 V ripple-free d.c. for special applications;

• –        constant voltage isolating transformers covered by this part 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 a.c. or 120 V ripple-free d.c.;

• –        constant voltage safety isolating transformers covered by this part 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 part 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 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.) may be necessary;

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

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

• –         additional requirements in accordance with other appropriate standards and national rules may be applicable to transformers intended for use in special environments.

NOTE 4 Future technological development of transformers may necessitate a need to increase the upper limit of the frequencies, until then this part may be used as a guidance document.