1 Scope

1.1 This International Standard deals with all aspects of safety (such as electrical, thermal and mechanical) of:
a)Stationary or portable, single-phase or polyphase, air-cooled (natural or forced) isolating and safety isolating transformers, associated or otherwise, having a rated supply voltage not exceeding 1 000 V a.c. and rated frequency not exceeding 1 MHz, the rated output not exceeding the following values.

NOTE 1 - For higher frequencies, this standard may be used as a guidance document. For isolating transformers:
- 25 kVA for single-phase transformers;
- 40 kVA for polyphase transformers.

For safety isolating transformers:
- 10 kVA for single-phase transformers;
- 16 kVA for polyphase transformers.
The no-load output voltage and rated output voltage do not exceed:
- for isolating transformers 500 V a.c. or 708 V ripple free d.c.

NOTE 2 - For isolating transformers, the no-load rated output voltage may be up to 1 000 V a.c. or 1 415 V ripple free d.c. to be in accordance with the national wiring rules or for special purposes.
- for safety isolating transformers 50 V a.c. r.m.s. and/or 120 V ripple free d.c. between conductors or between any conductor and earth.

NOTE 3 - Isolating and safety isolating transformers are used where double or reinforced insulation between circuits is required by the installation rules or by the appliance specification (for example toys, bells, portable tools, handlamps).

Rated values for each type of transformer are indicated in the relevant part 2.
b) Stationary or portable, single-phase or polyphase, air-cooled (natural or forced) separating transformers, auto-transformers, variable transformers and small reactors, associated or not, having a rated supply voltage not exceeding 1 000 V a.c., a rated frequency not exceeding 1 MHz, a rated no-load or load output voltage not exceeding 15 kV a.c. or d.c., and for independent transformers not less than 50 V a.c. and/or 120 V ripple free d.c. and a rated output not exceeding the following values:
- 1 kVA for single-phase transformers;
- 2 kVAR for single-phase reactors;
- 5 kVA for polyphase transformers;
- 10 kVAR for polyphase reactors;
unless otherwise specified in the relevant part 2.

NOTE 1 - Separating transformers are used where double or reinforced insulation between circuits is not required by the installation rules or by the appliance specification.

NOTE 2 - The technological development of transformers might imply a need to increase the higher limit of the rated frequency.

NOTE 3 - Normally, the transformers are intended to be associated with equipment to provide voltages different from the supply voltage for the functional requirement of the equipment. The safety insulation may be provided (or completed) by other features of the equipment, such as the body. Parts of output circuits may be connected to the input circuit or to protective earth.
c) Power supply units incorporating a transformer of types a) or b).

NOTE 1 - This may include units for transforming, rectifying, converting, frequency inverting or their combinations intended for power supplying electrical equipment, except for switch-mode power supplies.

NOTE 2 - Examples of power supply units are transformers, battery eliminators and converters for building-in or self-contained. In the latter case they can even be provided with integrated pins, intended to be introduced into fixed socket-outlets.

NOTE 3 - Requirements for transformers for switch-mode power supplies are contained in IEC 61558-2-17.