This part of IEC 61558 deals with safety aspects of transformers, reactors, power supply units and combinations thereof such as electrical, thermal and mechanical safety.

This document covers the following independent or associated stationary or portable types of dry-type transformers, power supply units, including switch mode power supply units, reactors and combinations thereof in the field of safety. The windings can be encapsulated or non-encapsulated. They are not forming a part of the distribution network.

NOTE 1 The distinction between transformers, power supply units and switch mode power supply units is as follows:

for transformers, there is no change in frequency. However, transformers (e.g. constant voltage transformers) can have an internal resonance frequency not exceeding 30 kHz;
for power supply units, the internal operational frequency and waveform are different from the supply frequency and waveform, and the internal operational frequency does not exceed 500 Hz (see definition 3.1.19);
for switch mode power supply units, the internal operational frequency and waveform are different from the supply frequency and waveform and the internal operational frequency exceeds 500 Hz and does not exceed 100 MHz.

The relevant parts of IEC 61558-2 can be found in the introduction of this document.

Stationary or portable, single-phase or poly-phase, air-cooled (natural or forced), isolating and safety isolating transformers, independent or associated with the following characteristics:
- rated supply voltage not exceeding 1 000 V AC;
- rated supply frequency not exceeding 500 Hz;
and complying with the following values, unless otherwise specified in the relevant part of IEC 61558-2:
1. for isolating transformers:
  - rated output for single phase transformers, not exceeding 25 kVA, and for polyphase transformers not exceeding 40 kVA;
  - no-load output voltage and the rated output voltage exceeding 50 V AC, and not exceeding 500 V a.c, or 1 000 V AC to be in accordance with the national wiring rules or for a special application.
for safety isolating transformers:
- rated output for single phase transformers not exceeding 10 kVA, and for polyphase transformers not exceeding 16 kVA;
- no-load output voltage and the rated output voltage not exceeding 50 V AC between conductors, or between any conductor and protective earthing.
NOTE 2 Isolating and safety isolating transformers are used where double or reinforced insulation between circuits is required by the installation rules or by the appliance specification (for example toys, bells, portable tools, handlamps).
Stationary or portable, single-phase or polyphase, air-cooled (natural or forced) separating transformers, auto-transformers, variable transformers and small reactors, independent or associated with the following characteristics:
- rated supply voltage not exceeding 1 000 V AC;
- rated supply frequency not exceeding 500 Hz;
and complying with the following values, unless otherwise specified in the relevant part of IEC 61558-2:
- no-load output voltage or a rated output voltage for both independent and associated transformers not exceeding 15 kV AC, and for independent transformers, a rated output voltage not less than 50 V AC;
- rated output not exceeding the following values:
  1. 1 kVA for single-phase transformers;
  2. 2 kVAR for single-phase reactors;
  3. 5 kVA for polyphase transformers;
  4. 10 kVAR for polyphase reactors.
NOTE 3 Separating transformers are used where double or reinforced insulation between circuits is not required by the installation rules or by the appliance specification.

NOTE 4 Normally, the transformers of type b) are intended to be associated with the equipment to provide voltages different from the supply voltage for the functional requirements of the equipment. The protection against electric shock can be provided or completed by other features of the equipment, such as the body. Parts of output circuits can be connected to the input circuit or to the protective earthing.
Stationary or portable, single-phase or polyphase, air-cooled (natural or forced), independent or associated power supply units and switch mode power supply units incorporating one or more transformer(s) of type a) or b) with the following characteristics:
- rated supply voltage not exceeding 1 000 V AC;
- rated supply frequency not exceeding 500 Hz;
- internal operational frequency for power supply units not exceeding 500 Hz and for switch mode power supply units not exceeding 100 MHz;
and with the following values, unless otherwise specified in the relevant part of IEC 61558- 2:
1. for power supply units and switch mode power supply units incorporating isolating transformers:
  - rated output for single- phase or polyphase power supply units or switch mode power supply units not exceeding 1 kVA;
  - no-load output voltage and the rated output voltage exceeding 50 V AC or 120 V ripple-free DC, and not exceeding 500 V AC or 708 V ripple-free DC, or 1 000 V AC or 1 415 V ripple- free DC to be in accordance with national wiring rules or for a special application;
2. for power supply units and switch mode power supply units incorporating safety isolating transformers:
  - rated output for single- phase or polyphase power supply units and switch mode power supply units not exceeding 1 kVA;
  - no-load output voltage and rated output voltage not exceeding 50 V AC or 120 V ripple-free DC between conductors, or between any conductor and protective earthing.
  NOTE 5 Power supply units and switch mode power supply units incorporating isolating and safety isolating transformers are used where double or reinforced insulation between circuits is required by the installation rules or by the appliance specification (for example toys, bells, portable tools, handlamps).
3. for power supply units and switch mode power supply units incorporating separating transformers, auto-transformers , and variable transformers:
  - rated output for single-phase or polyphase power supply units and switch mode power supply units not exceeding 1 kVA;
  - no-load output voltage and rated output voltage for both, independent and associated transformers not exceeding 15 kV AC, and for independent transformers, a rated output voltage not less than 50 V AC.
NOTE 6 Power supply units and switch mode power supply units incorporating separating transformers are used where double or reinforced insulation between circuits is not required by the installation rules or by the appliance specification.

This document also applies to transformers, power supply units, switch mode power supply units and reactors incorporating electronic circuits.

This document is applicable to transformers without limitation of the rated output subject to an agreement between the purchaser and the manufacturer.

This document does not apply to external circuits and their components intended to be connected to the input or output terminals or socket-outlets of the transformers, power supply units and switch mode power supply units, and reactors.

Attention is drawn to the following:

for transformers intended to be used in vehicles, on board ships, and 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 like fungus, vermin, termites, solar-radiation, and icing are considered;
the different conditions for transportation, storage, and operation of the transformers should also be considered;
additional requirements in accordance with other appropriate standards and national rules can be applicable to transformers intended for use in special environments, such as tropical environments.

Future technological development of transformers can necessitate a need to increase the upper limit of the frequencies; until then this document can be used as a guidance document.

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PDF Pages	PDF Title
2	undefined
5	Annex ZA(normative)Normative references to international publicationswith their corresponding European publications
11	Annex ZZ(informative)Relationship between this European standard and the safety objectives of Directive 2014/35/EU [2014 OJ L96] aimed to be covered
13	English CONTENTS
20	FOREWORD
22	INTRODUCTION
23	Figures Figure 1 – IEC 61558 principle
25	1 Scope
27	2 Normative references
30	3 Terms and definitions
31	3.1 Transformers
34	3.2 General terms
35	3.3 Operations and protections
37	3.4 Circuits and windings
38	3.5 Ratings
40	3.6 No-load values 3.7 Insulation
44	3.8 Touch current and protective earthing conductor current 4 General requirements
45	5 General notes on tests
46	Figure 2 – Mounting box for flush-type transformer
47	6 Ratings 7 Classification
48	8 Marking and other information
52	Tables Table 1 – Symbols used on equipment or in instructions
54	9 Protection against electric shock 9.1 General
55	9.2 Protection against contact with hazardous-live-parts 9.2.1 Determination of hazardous-live-parts 9.2.2 Accessibility to hazardous-live-parts
56	Figure 3 – Test pin (see IEC 61032, test probe 13)
57	Figure 4 – Standard test finger (see IEC 61032, test probe B)
58	9.2.3 Accessibility to non hazardous-live-part 9.3 Protection against hazardous electrical discharge 10 Change of input voltage setting
59	11 Output voltage and output current under load
60	12 No-load output voltage 13 Short-circuit voltage 14 Heating 14.1 General requirements 14.1.1 Temperature-rise test
62	14.1.2 Alternative temperature-rise test
64	Figure 5 – Example of back-to-back method – Single phase Figure 6 – Example of back-to-back method – Three phase
65	14.1.3 Determination of steady-state conditions Table 2 – Values of maximum temperatures in normal use
66	14.2 Application of 14.1 or 14.3 according to the insulation system Table 3 – Explanation of the maximum winding temperatures required in Table 2
67	14.3 Accelerated ageing test for undeclared class of insulation system 14.3.1 General 14.3.2 Heat run Table 4 – Test temperature and testing time (in days) per cycle
68	14.3.3 Vibration 14.3.4 Moisture treatment 14.3.5 Measurements 15 Short circuit and overload protection 15.1 General requirements 15.1.1 Short circuit and overload test method
70	Table 5 – Maximum values of temperatures under short-circuitor overload conditions
71	15.1.2 Alternative short circuit and overload test method 15.2 Inherently short-circuit proof transformers 15.3 Non-inherently short-circuit proof transformers Table 6 – Values of T and k for fuses
72	15.4 Non-short-circuit proof transformers 15.5 Fail-safe transformers
73	16 Mechanical strength 16.1 General 16.2 Stationary transformers
74	16.3 Portable transformers (except portable transformers with integral pins for introduction in socket-outlet in the fixed wiring) 16.4 Portable transformers provided with integral pins for introduction in socket-outlets of the fixed wiring 16.4.1 General requirements
75	16.4.2 Portable transformers provided with integral pins according to EN 50075 (IEC plug type C) for introduction in socket-outlets of the fixed wiring Table 7 – Pull force on pins
76	16.5 Additional requirements for transformers to be used in vehicles and railway applications 16.5.1 Transformers to be used in vehicles and railway applications Table 8 – Conditions for vibration testing (random) Table 9 – Amplitude spectrum density ASD values for accelerated life testing
77	16.5.2 Test requirements for the transportation of transformers Figure 7 – Amplitude spectrum density for random testing Table 10 – Frequency values depending on the weight of the specimen Table 11 – Excitation values for vibration testing
78	17 Protection against harmful ingress of dust, solid objects and moisture 17.1 Degrees of protection provided by enclosures (IP code) 17.1.1 General requirements Figure 8 – Normalised spectrum of shock
79	17.1.2 Tests on transformers with enclosure
80	Table 12 – Solid-object-proof transformer test
81	17.2 Humidity treatment
82	18 Insulation resistance, dielectric strength and leakage current 18.1 General 18.2 Insulation resistance
83	18.3 Dielectric strength test Table 13 – Values of insulation resistance
84	Table 14 – Table of dielectric strength test voltages
85	18.4 Insulation between and within windings 18.5 Touch current and protective earthing conductor current 18.5.1 General Figure 9 – Test voltage sequence
86	18.5.2 Touch current
87	18.5.3 Protective earthing conductor current Figure 10 – Test configuration: single-phase equipment on star TN or TT system Table 15 – Limits for currents
88	19 Construction 19.1 General construction 19.1.1 General 19.1.2 Auto-transformers
89	19.1.3 Separating transformers
90	19.1.4 Isolating transformers and safety isolating transformers
92	19.2 Flammability of materials 19.4 Class II transformer contact prevention of accessible conductive parts 19.5 Class II transformer insulation reassembling after service
93	19.6 Loosening of wires, screws or similar parts 19.7 Resistor or capacitor connection with accessible conductive parts 19.8 Bridging of separated conductive parts by resistors or capacitors
94	19.9 Insulating material separating input and output windings 19.10 Accidental contact protection against hazardous-live-parts provided by isolating coating
95	19.11 Insulating material of handles, operating levers, knobs and similar parts 19.12 Winding construction Figure 11 – Abrasion resistance test for insulating coated layers
99	19.13 Fixing of handles, operating levers and similar parts 19.14 Fixing of covers providing protection against electric shock
100	19.15 Strain on fixed socket-outlets caused by pin-transformers connection 19.16 Portable transformers for use in irregular or harsh conditions 19.17 Drain hole of transformers protected against ingress of water 19.18 Plug connected transformers protected against ingress of water 19.19 Flexible cable or flexible cord connection for class I portable transformers 19.20 SELV- and PELV-circuit separation of live parts
101	19.21 Protection against contact for FELV-circuit 19.22 Protective earthing regarding class II transformers
102	19.23 Protective earthing regarding class III transformers 20 Components
107	21 Internal wiring 22 Supply connection and other external flexible cables or cords
109	Table 16 – Nominal cross-sectional areas of external flexible cables or cords
111	Figure 12 – Flexing test apparatus
113	Table 17 – Pull and torque to be applied to external flexible cables or cords fixed to stationary and portable transformers
114	23 Terminals for external conductors
115	24 Provisions for protective earthing
117	25 Screws and connections
118	Table 18 – Torque to be applied to screws and connections
119	26 Creepage distances, clearances and distances through insulation 26.1 General Table 19 – Torque test on glands
120	26.2 Creepage distances and clearances 26.2.1 General 26.2.2 Windings covered with adhesive tape 26.2.3 Uncemented insulationing parts 26.2.4 Cemented insulating parts
121	26.2.5 Enclosed parts (e.g. by impregnation or potting)
122	26.3 Distance through insulation
125	Figure 13 – Test arrangement for checking mechanical withstanding of insulating materials in thin sheet layers
126	Table 20 – Clearances in mm
127	Table 21 – Creepage distances in mm
128	Table 22 – Distance through insulation in mm
129	Table 23 – Creepage distances and clearance between terminals for external connection
131	Table 24 – Values of FIW wires with minimum overall diameter and minimum test voltages according to the total enamel increase
133	27 Resistance to heat, fire and tracking 27.1 General 27.2 Resistance to heat 27.2.1 General 27.2.2 External accessible parts Figure 14 – Ball-pressure apparatus
134	27.2.3 Internal parts 27.3 Resistance to abnormal heat under fault conditions
135	27.4 Resistance to fire 27.4.1 General
136	27.4.2 External accessible parts 27.4.3 Internal parts
137	27.5 Resistance to tracking 28 Resistance to rusting
138	Annexes Annex A (normative) Measurement of creepage distances and clearances Figure A.1 – Example 1 Table A.1 – Width of groove values depending on the pollution degree
139	Figure A.2 – Example 2 Figure A.3 – Example 3 Figure A.4 – Example 4
140	Figure A.5 – Example 5 Figure A.6 – Example 6
141	Figure A.7 – Example 7 Figure A.8 – Example 8
142	Annex B (normative) Testing a series of transformers B.1 General B.2 Requirements
143	B.3 Constructional inspection
144	Annex C (void)
145	Annex D (void)
146	Annex E (normative) Glow-wire test E.1 General E.2 Severity E.3 Conditioning E.4 Test procedure
147	Annex F (normative) Requirements for manually operated switches which are parts of transformers assembly F.1 General F.2 Switches tested as a separate component F.3 Switches tested as part of the transformer
148	Table F.1 – Peak surge current of additional loads
150	Annex G (normative) Tracking test G.1 General G.2 Test specimen G.3 Test apparatus G.4 Procedure
151	Annex H (normative) Electronic circuits H.1 General H.2 General notes on tests (addition to Clause 5) H.3 Short circuit and overload protection (addition to Clause 15)
153	H.4 Creepage distances, clearances and distances through insulation (addition to Clause 26)
154	Figure H.1 – Example of an electronic circuit with low-power points
155	Annex I (informative) Dimensions for rectangular cross-section connectors of transformers, basic dimensions and coordination Table I.1 – Dimensions of rectangular copper connectors
157	Annex J (normative) Measuring network for touch-currents Figure J.1 – Measuring network for touch-current
158	Annex K (normative) Insulated winding wires K.1 General K.2 Type tests K.2.1 General K.2.2 Dielectric strength test K.2.3 Flexibility and adherence
159	K.2.4 Heat shock K.2.5 Retention of dielectric strength after bending Table K.1 – Mandrel diameter Table K.2 – Oven temperature
160	K.3 Testing during manufacturing K.3.1 General K.3.2 Routine test K.3.3 Sampling test
161	Annex L (normative) Routine tests (production tests) L.1 General L.2 Protective earthing continuity test L.3 Checking of no-load output voltage L.4 Dielectric strength test
162	L.5 Checking of protective devices mounting L.6 Visual inspection L.7 Repetition test after routine dielectric strength test
163	Annex M (informative) Examples to be used as a guide for 19.1 M.1 General M.2 Coil-former M.2.1 Concentric type Figure M.1 – Examples for concentric type constructions
164	M.2.2 Side-by-side type M.3 Windings M.3.1 Without screen Figure M.2 – Examples for side-by-side type constructions Figure M.3 – Examples for winding constructions without screen
165	M.3.2 With screen Figure M.4 – Examples for wrapped winding constructions Figure M.5 – Examples for winding constructions with screen
166	Annex N (informative) Examples for checking points of dielectric strength test voltages
167	Figure N.2 – Transformer of class II construction with metal enclosure Figure N.3 – Transformer of class II construction with enclosure of insulating material
168	Annex O (void)
169	Annex P (informative) Examples for measurement points of creepage distances and clearances Figure P.1 – Transformer of class I construction
170	Figure P.2 – Transformer of class I construction with earthed metal screen Figure P.3 – Transformer of class II construction with metal enclosure
171	Figure P.4 – Transformer of class II construction with enclosure of insulating material
172	Annex Q (informative) Explanation of IP numbers for degrees of protection Q.1 General Q.2 Degrees of protection against access to hazardous parts and against solid foreign objects
173	Table Q.1 – Degrees of protection against access to hazardous parts indicated by the first characteristic numeral Table Q.2 – Degrees of protection against solid foreign objects indicated by the first characteristic numeral
174	Q.3 Degrees of protection against ingress of water Table Q.3 – Degrees of protection indicated by the second characteristic numeral
175	Annex R (normative) Explanations of the application of 6.1.2.2.1 of IEC 60664-1:2007 R.1 Impulse dielectric test R.2 Example Table R.1 – Impulse test voltage according to 6.1.2.2.1 of IEC 60664-1:2007
177	Annex S (void)
178	Annex T (void)
179	Annex U (void)
180	Annex V (informative) Symbols to be used for thermal cut-outs V.1 General V.2 Non-self-resetting thermal cut-out (see 3.3.4) V.3 Self-resetting thermal cut-out (see 3.3.3) Figure V.1 – Restored by manual operation Figure V.2 – Restored by disconnection of the supply Figure V.3 – Thermal link (see 3.3.5) Figure V.4 – Self-resetting thermal cut-out
181	Annex W (normative) Coated printed circuit boards W.1 Preamble W.2 General W.3 Cold W.4 Rapid change of temperature W.5 Additional tests
182	Bibliography
184	Index of defined terms

Published By	Publication Date	Number of Pages
BSI	2019	186


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Status	Definitive
Pages	186
Publication Date	2019-06-25
ISBN	978 0 580 91205 4
Standard Number	BS EN IEC 61558-1:2019
Title	Safety of transformers, reactors, power supply units and combinations thereof – General requirements and tests
Identical National Standard Of	IEC 61558-1:2017, EN 61558-1 Ed3.0
Replaces	BS EN 61558-1:2005+A1:2009
Descriptors	Polyphase transformers, Windings, Flexible conductors, Single-phase transformers, Portable, Type testing, Clearance distances, Electrical insulation, Electric terminals, Small-power transformers, Drop tests, Tracking tests, Safety isolating transformers, Power output, Electric enclosures, Screws (bolts), Fire tests, Symbols, Earthing, Environmental testing, Rated voltage, Corrosion tests, Classification systems, Circuits, Electric power systems, Safety measures, Electrical testing, Transformers, Dielectric-strength tests, Short-circuit current tests, Dry-type transformers, Switches, Protected electrical equipment, Marking, Electrical protection equipment, Resistance measurement, Torque, Temperature-rise limit, Power transformers, Electrical safety, Rated frequencies, Overload protection, Mechanical testing, Stationary, Isolating transformers, Alternating-current transformers, Dielectric strength, Cut-out devices, Leakage paths, Impact testing, Thermal testing, Electrical equipment, Cable glands
Publisher	BSI
Committee	PEL/96
ICS Codes	29.180 - Transformers. Reactors

BS EN IEC 61558-1:2019

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BS EN IEC 61558-1:2019