The CEI (Comitato Elettrotecnico Italiano) – Italian Electrotechnical Committee

This page provides an overview of some of the standards transposed from the international IEC 61558 standard by CEI Technical Committee 96.

In accordance with the internal regulation of the CEN/CENELEC, national committees that are members of CENELEC are required to adopt the European regulation as a national standard, and with no modifications (IEC EN 61558-1-2 …).

CEI EN 61558-1 (classification CEI 96-3) Safety of transformers and power supply units and similar products.

This standard establishes the general safety criteria and tests for transformers and power-supply units.

CEI EN 61558-2-1 CEI EN 61558-2-1 Separating transformers for general use (not resistant to short circuits).

This standard applies to transformers for which installation rules or specifications of the device do not require the presence of double or reinforced isolation between circuits. The safety isolation may be provided (or completed) by other characteristics of the equipment, such as the ground (earth) connection.

CEI EN 61558-2-2 Control transformers (not resistant to short circuits.

This standard applies to separating transformers for use in the power supply to control circuits (e.g. signalling, controlling, interlocking etc …). The main isolation must be multiplied by a factor of 1.4.

CEI EN 61558-2-4 Isolation transformers for general use (not resistant to short circuits).

This standard applies to those transformers used when the installation regulations require a separation of circuits with double or reinforced isolation (mobile tools, lawn mowers etc).

CEI EN 61558-2-6 Safety transformers for general use (not resistant to short circuits).

In practice these are isolation transformers the no-load secondary voltage of which must not exceed an effective value of 50Vac or 120V flat DC. With a no-load secondary voltage not exceeding a peak value of 35V the live parts can be accessed.

CEI EN 61558-2-13 General-purpose auto-transformers (not resistant to short circuits).

This standard applies to transformers in which no isolation is required by electrical system rules or by the specifications of the device.

CEI EN 61558-2-15 Isolation transformers for medical use (not resistant to short circuits).

These are isolation transformers that have to be installed in the immediate vicinity of operational medical units, either internally or externally.
The nominal secondary voltage of these transformers must never exceed 250VAC in both single-phase and three-phase systems.
The single-phase isolation transformers for medical use must have a power rating never lower than 0.5 KVA and never higher than 10 KVA.

CEI EN 61558-2-20 Particular requirements for small reactors.

This provision refers to devices with one or more windings which function in accordance with the principle of self-induction, according to which an electrical current generates a magnetic field through a core presenting good magnetic permeability or through the air.