1 Scope

Replacement: This International Standard deals with all aspects of safety such as electrical, thermal and mechanical.

This part 2-13 of IEC 61558 applies to stationary or portable, single-phase or polyphase, aircooled (natural or forced), independent or associated auto-transformers, having a rated supply voltage not exceeding 1 000 V a.c., a rated frequency not exceeding 500 Hz.

The core power does not exceed:
- 1 kVA for single-phase auto-transformers;
- 5 kVA for polyphase auto-transformers.
The rated output does not exceed:
- 20 kVA for single-phase auto-transformers;
- 100 kVA for polyphase auto-transformers.

This standard is also applicable to auto-transformers having a core power up to 40 kVA, however such transformers are considered as special transformers and are subjected to an agreement between the purchaser and the supplier. Such special auto-transformers have no limitation for the rated output.

The no-load output voltage and the rated output voltage do not exceed 1 000 V a.c. or 1 415 V ripple-free d.c.

For independent auto-transformers, the no-load output voltage and the rated output voltage are not less than 50 V a.c. or 120 V ripple free d.c.

This standard is applicable to transformers where no insulation between circuits is required by the installation rules or by the equipment specifications.

NOTE 1 - Normally, the transformers are intended to be associated with equipment to provide voltages different from the supply voltage for the functional requirements of the equipment. The safety insulation may be provided by other features of the equipment, such as the body. This standard is applicable to dry-type transformers. The windings may be encapsulated or non-encapsulated.

NOTE 2 - For transformers filled with liquid dielectric or pulverised material, such as sand, requirements are under consideration.

NOTE 3 - Attention is drawn to the fact that:
- for transformers intended to be used in vehicles or on board ships or aircraft, additional requirements may be necessary;
- for transformers intended to be used in tropical countries, special requirements may be necessary;
- in locations where special environmental conditions prevail, particular requirements may be necessary.