scope:

This International Standard covers such aspects of safety as electrical, thermal and mechanical.

This Part 2-9 of IEC 61558 applies to stationary or portable single-phase air-cooled (natural or forced) associated safety isolating transformers for class III handlamps for tungsten filament lamps, having a rated supply voltage not exceeding 1 000 V a.c., a rated frequency not exceeding 500 Hz and a rated output not exceeding 10 kVA.

Transformers for class III handlamps for tungsten filament lamps

 − have a no-load output voltage and a rated output voltage not exceeding 50 V a.c. or 120 V ripple-free d.c.;

 − are used where double or reinforced insulation between circuits is required by the installation rules or by the appliance specification;

 − have a low variation between no-load and rated output voltage;

 − have a limited output voltage.

This standard is applicable to dry-type transformers. The windings may be encapsulated or non-encapsulated.

NOTE 1  For transformers filled with liquid dielectric or pulverised material, such as sand, additional requirements are under consideration.

NOTE 2  Attention is drawn to the fact that

 - 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;

 - for transformers intended for use in tropical areas, measures to protect the enclosure and the components inside the enclosure against external influences like fungus, vermin and termites should also be considered;

 - in locations where special environmental conditions prevail, additional requirements (from other applicable standards, national rules, etc.) may be necessary.

This standard also applies to transformers incorporating electronic circuits. This standard does not apply to external circuits and their components intended to be connected to the input and output terminals or socket-outlets of the transformer.