This part of 61558 deals with safety aspects of control transformers and power supplies
incorporating control transformers such as electrical, thermal and mechanical safety.
This Part 2-2 is applicable to control transformers and power supplies incorporating both
control transformers and electronic circuits. This Part 2-2 is not applicable to external
circuits and their components intended to be connected to the input terminals, output terminals
or socket-outlets of the transformer and power supplies.
This Part 2-2 does not apply to transformers covered by 60076-11.
This Part 2-2 applies to stationary or portable, single-phase or poly-phase, air-cooled (natural
or forced), independent or associated control transformers and power supplies
incorporating a control transformer, having a rated supply voltage not exceeding 1 000 V
a.c. and rated supply and internal operating frequency not exceeding 500 Hz.
The rated thermal output does not exceed:
- 25 kVA for single-phase control transformers and power supplies incorporating control
transformers;
- 40 kVA for poly-phase control transformers and power supplies incorporating control
transformers.
This Part 2-2 is applicable to control transformers and power supplies incorporating control
transformers without limitation of the rated output subject to an agreement between the
purchaser and the manufacturer.
This Part 2-2 is applicable to dry-type transformers. The windings may be encapsulated or
non-encapsulated.
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.
For independent control transformers and independent power supplies incorporating
control transformers, the no-load output voltage and / or the rated output voltage is not
less than 50 V a.c., or 120 V ripple free d.c.
Control transformers covered by this Part 2-2 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.
NOTE 1: Normally, the control transformers and power supplies incorporating control transformers are
intended to be used with equipment to provide voltages different from the supply voltage for the functional requirements of the equipment. The protection against electric shock 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 circuits or to protective earth.
This Part 2-2 is applicable to control transformers and power supplies incorporating control
transformers associated with specific equipment, to the extent decided upon by the relevant
IEC technical committees.
NOTE 2: Attention is drawn to the following:
- for control transformers and power supplies incorporating control transformers intended to be used in
vehicles, on board ships and on board 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 control transformers and power supplies incorporating control transformers should also be considered;
- additional requirements in accordance with other appropriate standards and national rules may be applicable to control transformers and power supplies incorporating control transformers intended for use in special environments, such as tropical environments.
NOTE 3: Future technological development of control transformers and power supplies incorporating control transformers may necessitate a need to increase the upper limit of the frequencies, until then this Part 2-2 may be used as a guidance document.