EN 61558-1 covers safety rules for transformers. When the term transformer is used, the term includes transformers, reactors and power supplies, as applicable.
While creating EN 61558-1, the rules in IEC 60364 were taken into account to the extent possible. Therefore, transformers can be installed according to the installation rules in the standard in question. However, national plumbing regulations may differ.
In EN 61558-1, internationally accepted protection levels against possible electrical, mechanical and fire damage caused by transformers operated under normal conditions according to the manufacturer's instructions are taken into account. EN 61558-1 also covers unusual conditions that may be encountered in practice.
If a transformer conforming to EN 61558-1 is examined and tested and there are other issues that impair the safety level covered by these rules, it is not necessary to conclude that it complies with the safety principles of EN 61558-1.
A transformer containing different materials and different shapes than the materials and construction detailed in EN 61558-1 may be examined and tested in accordance with the spirit of the rules. If substantially equivalent, it can be concluded that it complies with the safety principles of EN 61558-1.
The standard regarding non-safety aspects of electromagnetic compatibility (EMC) of transformers is IEC 62041. However, EN 61558-1 also covers tests applicable to transformers that may be exposed to conditions involving safety concerns.
The purpose of EN 61558-1 is to provide rules and tests that are generally considered applicable to many transformer types and can be specified in the relevant sections of IEC 61558-2. Therefore, it should not be thought that EN 61558-1 only gives specific rules for any type of transformer. The provisions of EN 61558-1 apply only to certain types of transformers to the extent specified in the relevant part of IEC 61558-2.
EN 61558-1 may also include routine tests.
Each part of IEC 61558-2 together with EN 61558-1 contains all the necessary rules for the transformer covered and does not refer to other parts of IEC 61558-2. For transformers with IP00 protection index and connected transformers it is possible to have circuits of the same construction corresponding to the relevant parts of IEC 61558-2 (e.g. SELV output circuit according to IEC 61558-2-6 and 230 V output circuit according to IEC 61558-2-4). However, if the transformer is covered by different parts of IEC 61558-2, the relevant part of IEC 61558-2 shall apply to a reasonable extent for each function/application. If applicable, the impact of one function on another is taken into account.
If a suitable part of IEC 61558-2 is not available for a particular transformer or group of transformers, the nearest applicable part of IEC 61558-2 may be used as guidance for rules and tests.
Where a reference to IEC 61558-1 is made for the rules in any clause of IEC 61558-2 with a statement of the form "This clause of IEC 61558-1 applies", this expression means that all the rules of the relevant clause of IEC 61558-1 are applicable, except those rules which are not expressly applicable to the particular type of transformer covered in the relevant part of IEC 61558-2.
The principle for the preparation of the different parts of IEC 61558-2 is given in Figure 0.
The relevant clauses of EN 61558-1 (for example, clauses on the thermal resistance of windings) also apply to transformers that form part of a device and are not individually tested.
EN 61558-1; Covers safety aspects of power transformers, power supplies, reactors and similar products, such as electrical, thermal and mechanical safety:
EN 61558-1; It covers the following types of dry-type transformers, power supplies, including switching-mode power supplies, and reactors with or without enclosed windings:
Note 1 - The difference between transformers, power supplies and switching mode power supplies is as follows:
- There is no change in frequency in transformers. However, transformers (e.g. constant voltage transformers) may have an internal resonance frequency not exceeding 30 kHz,
- In power supplies, the internal operating frequency and waveform are different from the supply frequency and waveform and the internal operating frequency does not exceed 500 Hz (Article 3.1.19),
- In switching mode power supplies, the internal operating frequency and waveform are different from the supply frequency and waveform, and the internal operating frequency exceeds 500 Hz, but does not exceed 100 MHz.
Relevant parts of IEC 61558-2 are given in the Introduction.
a) Fixed or portable, single-phase or multi-phase, air-cooled (natural or forced), independent or connected isolating and safety isolating transformers that do not form part of the distribution network and have the following characteristics:
- Rated supply voltage not exceeding 1000 V a.c.,
- Rated supply frequency not exceeding 500 Hz,
Unless otherwise stated in the relevant section of IEC 61558-2, providing the following values;
• For isolating transformers:
- The rated output does not exceed 25 kVA for single-phase transformers and 40 kVA for multi-phase transformers,
- No-load output voltage and rated output voltage exceeding 50 V a.c., but not exceeding 500 V a.c. or 1000 V a.c., in accordance with the National Installation Regulations or a special application.
• For safety isolating transformers:
- The rated output does not exceed 10 kVA for single-phase transformers and 16 kVA for multi-phase transformers,
- The no-load output voltage and the rated output voltage, between conductors or between any conductor and protective earth, not exceeding 50 V a.c.
Note 1 – Where double or reinforced insulation between circuits is required due to installation rules or device characteristics (e.g. toys, bells, portable instruments, hand lamps), isolating and safety isolating transformers are used.
b) Fixed or portable, single-phase or multi-phase, air-cooled (natural or forced), independent or connected isolating transformers, autotransformers, variable transformers or reactors that do not form part of the distribution network and have the following characteristics:
- Rated supply voltage not exceeding 1000 V a.c.,
- Rated supply frequency not exceeding 500 Hz,
Unless otherwise stated in the relevant section of IEC 61558-2, providing the following values;
- The no-load output voltage or rated output voltage for both independent and connected transformers does not exceed 15 kV a.c. and the declared output voltage for independent transformers is not less than 50 V a.c.
- Declared outputs not exceeding the following values;
- 1 kVA for single-phase transformers,
- 2 kVAR for single phase reactors,
- 5 kVA for multiphase transformers,
- 10 kVAR for multiphase reactors.
Note 2 – Splitter transformers are used where double or reinforced insulation between circuits is not required due to installation rules or device features.
Note 3 – Normally, transformers of the type given in point b) are intended to be connected with equipment to provide voltages different from the supply voltage due to the functional characteristics of the equipment.
Protection against electric shock may be provided or supplemented by other parts of the equipment, such as the housing. Portions of the output circuits can be connected to the input circuit or to protective ground.
c) Independent or connected power supplies and switching mode power supplies, fixed or portable, single-phase or multi-phase, air-cooled (natural or forced), not forming part of the distribution network and containing one or more transformers of the type given in a) or b) with the following characteristics:
- Rated supply voltage not exceeding 1000 V a.c.,
- 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 stated in the relevant section of IEC 61558-2, providing the following values;
• For power supplies containing isolating transformers and switching mode power supplies:
- Single-phase or multiphase power supplies or switching mode power supplies whose rated output does not exceed 1 kVA,
- Idle output voltage and rated output voltage; Depending on the National Installation Regulations or a specific application, exceeding 50 V a.c. or 120 V ripple-free d.c., but not exceeding 500 V a.c. or 708 V ripple-free d.c. or 1000 V a.c. or 1415 V ripple-free d.c.
• For power supplies and switching mode power supplies containing safety isolating transformers:
- Single-phase or multiphase power supplies or switching mode power supplies whose rated output does not exceed 1 kVA,
- Idle output voltage and rated output voltage; not exceeding 50 V a.c. or 120 V ripple-free d.c. between conductors or between any conductor and protective earth.
Note 4 – Where double or reinforced insulation between circuits is required due to installation rules or device characteristics (e.g. toys, bells, portable instruments, hand lamps),
Power supplies containing isolating and safety isolating transformers and switching mode power supplies are used.
• For power supplies and switching mode power supplies containing isolating transformers, autotransformers, and variable transformers:
- Single-phase or multiphase power supplies or switching mode power supplies whose rated output does not exceed 1 kVA,
- The no-load output voltage or rated output voltage for both independent and connected transformers does not exceed 15 kV a.c. and the declared output voltage for independent transformers is not less than 50 V a.c.
Note 5 – Where double or reinforced insulation between circuits is not required due to installation rules or device characteristics, power supplies incorporating isolating transformers and switching mode power supplies are used.
d) EN 61558-1 is also applicable to transformers marked tw whose rated output does not exceed 1000 VA. Here, tw temperature does not exceed 140 oC (tw 140). However, marking transformers as tw is optional.
EN 61558-1; It also includes transformers, power supplies, switching mode power supplies and reactors containing electronic circuits.
EN 61558-1 does not apply to external circuits or components intended for connection to input and output terminals or receptacles of transformers, power supplies, switching mode power supplies and reactors.
Note 6 – The following points should be taken into consideration:
- Additional rules (from other applicable standards or national regulations, etc.) may be required for transformers intended for use in vehicles, ships or aircraft;
- The enclosure and the components inside the enclosure; Protective measures against fungi, insects, ants, solar radiation and icing must also be taken into account,
- Different conditions for transportation, storage and operation of the transformer must also be taken into account,
- For transformers intended for use in special environments such as tropical regions, additional requirements may be required in accordance with other appropriate standards and national rules.
Note 7 – Future technological developments of transformers may require increasing the upper limits of frequencies, henceforth; EN 61558-1 can be used as a guidance document.
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