EN 61558-1 covers safety rules for transformers. When the term transformer is used, it applies to transformers, reactors, and power supplies where applicable.
When EN 61558-1 was created, the rules in IEC 60364 were considered as much as possible. Therefore, transformers can be installed according to the basic installation rules in that standard. However, national installation regulations may vary.
EN 61558-1 considers international accepted levels of protection against fire damage caused by transformers operating under normal conditions, based on electrical, mechanical, and manufacturer's instructions. EN 61558-1 also includes unusual conditions that may be encountered in practice.
If a transformer that is conforming to EN 61558-1 does not comply with the safety levels covered by these rules when examined and tested, it is not necessary to conclude that it complies with the safety principles of EN 61558-1.
If a transformer contains materials or designs different from those detailed in EN 61558-1, it can be tested and examined according to the essence of the rules and if found equivalent, it may be considered compliant with the safety principles of EN 61558-1.
The standard for electromagnetic compatibility (EMC) of transformers is IEC 62041. However, EN 61558-1 also includes tests for transformers exposed to conditions affecting safety.
The purpose of EN 61558-1 is to provide rules and tests applicable to many types of transformers that are considered generally applicable and specified in the relevant sections of IEC 61558-2. Therefore, EN 61558-1 should not be considered as only giving specific rules for a particular type of transformer. The rules in EN 61558-1 only apply to specific transformer types as specified in the relevant section of IEC 61558-2.
EN 61558-1 includes routine tests.
The relevant sections of IEC 61558-2, together with EN 61558-1, include all necessary rules for transformers and do not refer to other sections of IEC 61558-2. Transformers with an IP00 protection rating and associated transformers can have identical circuits, as specified in IEC 61558-2, such as a SELV output circuit in accordance with IEC 61558-2-6 and a 230V output circuit in accordance with IEC 61558-2-4. However, if the transformer falls under a different section of IEC 61558-2, the appropriate section will be applied for each function or application, and where applicable, interactions between functions will be considered.
If a specific section of IEC 61558-2 does not exist for a particular transformer or group of transformers, the closest applicable section of IEC 61558-2 can be used as a guideline for rules and tests.
When a reference is made to IEC 61558-1 in the form of "This article of IEC 61558-1 applies," it means that all rules in the relevant article of IEC 61558-1 can be applied except where specific rules in the relevant section of IEC 61558-2 cannot be applied to a particular type of transformer.
The principle for the preparation of different sections of IEC 61558-2 is given in Figure 0.
The relevant articles of EN 61558-1 (for example, thermal resistance of windings) also apply to transformers that are parts of a device and have not been tested separately.
EN 61558-1 covers safety concerns such as electrical, thermal, and mechanical safety for power transformers, power supplies, reactors, and similar products.
EN 61558-1 covers dry type transformers, including switching mode power supplies and reactors, whether enclosed or unencased:
Note 1 - The difference between transformers, power supplies, and switching mode power supplies is as follows:
In transformers, there is no frequency change. However, transformers (for example, fixed voltage transformers) may have an internal resonant frequency not exceeding 30 kHz,
In power supplies, the internal operating frequency and waveform differ from the supply frequency and waveform, and the internal operating frequency does not exceed 500 Hz (see Article 3.1.19),
In switching mode power supplies, the internal operating frequency and waveform differ from the supply frequency and waveform, and the internal operating frequency exceeds 500 Hz but does not exceed 100 MHz.
The relevant sections of IEC 61558-2 are provided in the introduction.
a) Fixed or portable, single-phase or multiphase, air-cooled (natural or forced), separate or safely separated transformers that do not form part of a distribution network with the following characteristics:
Rated supply voltage not exceeding 1000V AC,
Rated supply frequency not exceeding 500 Hz,
Unless otherwise specified in the relevant section of IEC 61558-2, these characteristics must be met.
Note 1 – Separation and safety transformers are used where double or reinforced insulation is required between circuits due to installation rules or device features (for example; toys, bells, portable tools, hand lamps).
b) Fixed or portable, single-phase or multiphase, air-cooled (natural or forced), separate or attached transformers, auto-transformers, variable transformers or reactors with the following characteristics:
Rated supply voltage not exceeding 1000V AC,
Rated supply frequency not exceeding 500 Hz,
Unless otherwise specified in the relevant section of IEC 61558-2, these values should be met.
Note 2 – Separators are used where double or reinforced insulation is not required.
Note 3 – Typically, the transformers mentioned in item (b) are intended to be connected with equipment to provide a different voltage than the supply voltage.
Protection against electrical shock can be provided by the body or other parts of the equipment and can be completed by connections between circuits.
c) Fixed or portable, single-phase or multiphase, air-cooled (natural or forced), not part of a distribution network and having one or more of the types in item (a) or (b), including power supplies and switching mode power supplies with the following characteristics:
Rated supply voltage not exceeding 1000V AC,
Rated supply frequency not exceeding 500 Hz,
Internal operating frequencies not exceeding 500 Hz for power supplies and 100 MHz for switching mode power supplies,
Unless otherwise specified in the relevant section of IEC 61558-2, these characteristics should be met.
Note 4 – Separation and safety transformers are used where double or reinforced insulation is required between circuits due to installation rules or device features (for example; toys, bells, portable tools, hand lamps).
Note 5 – Separators are used where double or reinforced insulation is not required.
d) EN 61558-1 can also apply to transformers marked TW with a rated output of up to 1000 VA. Here, the TW temperature does not exceed 140 °C (TW 140). However, marking a transformer as TW is optional.
EN 61558-1 covers transformers, power supplies, switching mode power supplies, and reactors with electronic circuits.
EN 61558-1 does not apply to external circuits or components connected to the input and output terminals or sockets of transformers, power supplies, switching mode power supplies, and reactors.
Note 6 – Additional rules may be required for transformers designed for use in vehicles, ships, or aircraft under other relevant standards or national regulations.
Note 7 – Transformer technological developments may require increased frequency limits in the future, after which EN 61558-1 can be used as a guideline document.