CEI EN 61558-2-8

BILINGUAL

Replacement:

This part of IEC 61558 deals with the safety of bell and
chime transformers and power supply units
incorporating bell and chime transformers.
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 bell and chime
transformers and power supply units
incorporating bell and chime transformers.

This part is applicable to stationary,
single-phase, air-cooled (natural or forced)
independent or associated dry-type
transformers. The windings may be encapsulated or
nonencapsulated.

This standard is applicable to transformers and
power supply (linear).

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 takes precedence.

The rated supply voltage does not exceed 250 V
a.c., and the rated supply frequency and does not
exceed 500 Hz. This standard is applicable to
transformers and linear power
supply units with internal operating frequency not
exceeding 500 Hz.

The rated output shall not exceed 100 VA.

The no-load output voltage does not exceed 33 V
a.c. or 46 V ripple-free d.c., and the rated output
voltage does not exceed 24 V a.c., or 33 V ripple-free
d.c.

Bell and chime transformers are generally
intended to supply domestic sound signalling equipment and other
similar devices where the load is applied for short periods of
time.

NOTE 2 A partial load may be applied for illumination
purposes.

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.

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.

NOTE 3 Normally, the 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 is applicable to transformers
associated with specific equipment, to the extent decided upon by
the relevant IEC technical committees.

NOTE 4 Attention is drawn to the following:

– 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 transformer 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, such as tropical environment.

NOTE 5 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.