SIST EN IEC 62590-2-1:2026

SLOVENSKI STANDARD
01-april-2026
Železniške naprave - Elektronski močnostni pretvorniki za fiksne postroje - 2-1.
del: Enosmerni sistemi vleke - Nekrmiljeni usmerniki
Railway applications - Electronic power converters for fixed installations - Part 2-1: DC
traction applications - Uncontrolled rectifiers
Bahnanwendungen - Leistungselektronische Stromrichter für Ortsfeste Anlagen - Teil 2-
1: Anwendungen der Gleichstrom-Zugförderung - Diodengleichrichter
Applications ferroviaires - Convertisseurs électroniques de puissance pour installations
fixes - Partie 2-1: Applications de traction en courant continu - Redresseurs à diodes
Ta slovenski standard je istoveten z: EN IEC 62590-2-1:2026
ICS:
29.200 Usmerniki. Pretvorniki. Rectifiers. Convertors.
Stabilizirano električno Stabilized power supply
napajanje
45.040 Materiali in deli za železniško Materials and components
tehniko for railway engineering
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62590-2-1

NORME EUROPÉENNE
EUROPÄISCHE NORM February 2026
ICS 45.060.01
English Version
Railway applications - Electronic power converters for fixed
installations - Part 2-1: DC traction applications - Uncontrolled
rectifiers
(IEC 62590-2-1:2025)
Applications ferroviaires - Convertisseurs électroniques de Bahnanwendungen - Leistungselektronische Stromrichter
puissance pour installations fixes - Partie 2-1: Applications für Ortsfeste Anlagen - Teil 2-1: Anwendungen der
de traction en courant continu - Redresseurs non Gleichstrom-Zugförderung - Unkontrollierte Gleichrichter
commandés (IEC 62590-2-1:2025)
(IEC 62590-2-1:2025)
This European Standard was approved by CENELEC on 2026-01-23. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62590-2-1:2026 E

European foreword
The text of document 9/3224/FDIS, future edition 1 of IEC 62590-2-1, prepared by TC 9 "Electrical
equipment and systems for railways" was submitted to the IEC-CENELEC parallel vote and approved
by CENELEC as EN IEC 62590-2-1:2026.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2027-02-28
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2029-02-28
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 62590-2-1:2025 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 60076 (series) NOTE Approved as EN 60076 (series)
IEC 60076-1 NOTE Approved as EN 60076-1
IEC 60076-11 NOTE Approved as EN IEC 60076-11
IEC 60146-1-1 NOTE Approved as EN IEC 60146-1-1
IEC 60529 NOTE Approved as EN 60529
IEC 60909-0:2016 NOTE Approved as EN 60909-0:2016 (not modified)
IEC 61000-2-12 NOTE Approved as EN 61000-2-12
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 62695 - Railway applications - Fixed installations - EN 50329 -
Traction transformers
+A1 2010
IEC 62590-1 2025 Railway applications - Electronic power EN IEC 62590-1 2025
converters for fixed installations - Part 1:
General requirements
IEC 62590-2-1 ®
Edition 1.0 2025-12
INTERNATIONAL
STANDARD
Railway applications - Electronic power converters for fixed installations -
Part 2-1: DC traction applications - Uncontrolled rectifiers
ICS 45.060.01  ISBN 978-2-8327-0742-5

IEC 62590-2-1:2025-12(en)
IEC 62590-2-1:2025 © IEC 2025
CONTENTS
FOREWORD. 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, symbols and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Symbols . 9
3.3 Abbreviated terms . 9
4 System configurations and characteristics . 10
4.1 General . 10
4.2 Main interfaces . 10
4.3 Transformer main values . 11
4.3.1 General . 11
4.3.2 Impedance voltages . 11
4.3.3 Coupling factor . 12
4.4 Electrical connections . 13
4.5 Voltage characteristic . 14
4.6 Current characteristic . 15
4.7 Current imbalance . 16
4.8 Short time withstand capability . 16
4.9 Direct voltage harmonic content . 17
4.10 3AC power network harmonic current . 17
5 Design and integration . 17
5.1 General . 17
5.2 To be defined by user specification . 18
5.2.1 Electrical data . 18
5.2.2 Mechanical requirements . 19
5.3 To be indicated by manufacturer . 19
5.4 Marking . 20
5.4.1 Rating plate . 20
5.4.2 Main circuit terminals . 21
6 Tests . 21
6.1 General . 21
6.2 Test specifications . 22
6.2.1 Visual inspection . 22
6.2.2 Test of accessory and auxiliary components . 22
6.2.3 Insulation test . 23
6.2.4 Checking the protective functions . 23
6.2.5 Light load functional test . 23
6.2.6 Load test . 23
6.2.7 Inherent voltage drop . 23
6.2.8 Temperature-rise test . 25
6.2.9 Short time withstand current . 26
6.2.10 Power loss determination . 26
6.2.11 Audible sound . 27
6.2.12 Harmonic test . 27
IEC 62590-2-1:2025 © IEC 2025
6.2.13 Power factor measurement . 27
6.2.14 Mechanical test . 27
Annex A (informative) Determination of the voltage drop and the short-circuit currents
of uncontrolled rectifiers . 28
A.1 General . 28
A.2 Description of the method . 29
A.3 Example of a six-pulse rectifier or twelve-pulse rectifier with magnetically not
coupled transformer windings (K ≈ 0) . 34
A.4 Example of a twelve-pulse rectifier with closely coupled secondary windings
of the converter transformer (K ≈ 1) . 36
Annex B (informative) Examples of power factors of uncontrolled rectifiers . 39
B.1 General . 39
B.2 Considerations on the variation of the fundamental current and power factor
in rectifiers . 39
B.2.1 Basic considerations . 39
B.2.2 First working zone . 39
B.2.3 Second working zone . 40
Annex C (informative) Interphase transformer . 41
C.1 General . 41
C.2 Voltage and currents . 41
C.3 Intermittent current conditions . 42
C.4 Current imbalance . 42
Annex D (informative) Example of a protection curve . 43
Bibliography . 45

Figure 1 – General configuration . 10
Figure 2 – Reactances of a rectifier transformer . 11
Figure 3 – Voltage characteristic . 15
Figure 4 – Measurement of inherent voltage drop . 25
Figure A.1 – Typical characteristic of an uncontrolled rectifier . 29
Figure A.2 – External characteristics of six-pulse (three-phase bridge) rectifiers and
twelve-pulse rectifiers with magnetically non-coupled transformer windings (K = 0) . 32
Figure A.3 – External characteristics of twelve-pulse rectifiers with closely coupled
secondary windings of the converter transformer (K ≈ 1) . 33
Figure A.4 – Determination of the short-circuit currents of a six-pulse rectifier or a
twelve-pulse rectifier with magnetically not coupled transformer windings (K ≈ 0) . 36
Figure A.5 – Determination of the short-circuit currents of a twelve-pulse rectifier with
closely coupled transformer windings (K ≈ 1) . 38
Figure C.1 – Interphase transformer . 41
Figure D.1 – Example protection curve . 43

Table 1 – Connections and calculation factors for uncontrolled rectifiers . 14
Table 2 – Main rectifier design data . 18
Table 3 – Mechanical requirements . 19
Table 4 – Summary of tests . 22
Table A.1 – Method of use of the charts in Figure A.2 and Figure A.3 . 30
Table A.2 – Example of the application of Table A.1 for a six-pulse rectifier or a twelve-
pulse rectifier with magnetically not coupled transformer windings (K ≈ 0) . 34
Table A.3 – Example of the application of Table A.1 for a twelve-pulse rectifier with
closely coupled secondary windings of the converter transformer (K ≈ 1) . 37

IEC 62590-2-1:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Railway applications -
Electronic power converters for fixed installations -
Part 2-1: DC traction applications - Uncontrolled rectifiers

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 62590-2-1 has been prepared by IEC technical committee 9: Electrical equipment and
systems for railways. It is an International Standard.
This first edition of IEC 62590-2-1, in conjunction with the other parts of the IEC 62590 series,
cancels and replaces the first edition of IEC 62589 published in 2010 and the second edition of
IEC 62590 published in 2019.
This document includes the following significant technical changes with respect to IEC 62589
and the former IEC 62590:
a) Reduction of the requirements for uncontrolled rectifiers only;
b) Interface model for the different systems connected;
c) Energy efficiency addressed.
IEC 62590-2-1:2025 © IEC 2025
The text of this International Standard is based on the following documents:
Draft Report on voting
9/3224/FDIS 9/3265/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 62590 series, published under the general title Railway applications -
Fixed installations - Electronic power converters, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
IEC 62590-2-1:2025 © IEC 2025
INTRODUCTION
Electronic power converters for traction power supply differ from other converters for industrial
use due to special electrical service conditions and due to the large range of load variations
and the peculiar characteristics of the load.
For these reasons IEC 60146-1-1 does not fully cover the requirements of railway applications
and the decision was taken to have a specific standard for this use.
Uncontrolled rectifiers consist of a rectifier diode assembly and a transformer. Both fulfil
common requirements. The transformer determines the voltage versus current characteristic.
Converter transformers for fixed installations of railway applications are covered by IEC 62695.

IEC 62590-2-1:2025 © IEC 2025
1 Scope
This part of IEC 62590 describes functions and working principles, specifies requirements,
interfaces and test methods of uncontrolled rectifiers for DC electric traction power supply
systems. Uncontrolled rectifiers connect a 3AC power network with a DC electric traction system
with a unidirectional power flow using diode assemblies.
The coordination between the transformer and the rectifier diode assembly is included.
This document applies to fixed installations of following electric traction power supply systems:
• railway networks;
• metropolitan transport networks including metros, tramways, trolleybuses and fully
automated transport systems, magnetic levitated transport systems, electric road systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 62695, Railway applications - Fixed installations - Traction transformers
IEC 62590-1:2025, Railway applications - Electronic power converters for fixed installations -
Part 1: General requirements
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
3.1 Terms and definitions
3.1.1
semiconductor device
device whose essential characteristics are due to the flow of charge carriers within a
semiconductor
Note 1 to entry: The definition includes devices whose essential characteristics are only in part due to the flow of
charge carriers in a semiconductor but that are considered as semiconductor devices for the purpose of specification.
[SOURCE: IEC 60050-521:2002, 521-04-01]
3.1.2
rectifier
AC/DC converter for rectification
[SOURCE: IEC 60050-551:1998, 551-12-07, modified – The figure has been omitted.]
IEC 62590-2-1:2025 © IEC 2025
3.1.3
rectifier diode assembly
valve device assembly for rectification
Note 1 to entry: Often the term rectifier is used instead of rectifier diode assembly.
3.1.4
ideal no-load direct voltage
U
di
theoretical no-load mean direct voltage of a converter assuming no reduction by phase control,
no voltage drop in the assemblies, and no voltage rise at small loads
[SOURCE: IEC 60050-551:1998, 551-17-15, modified – “mean” has been added. “AC/DC” has
been removed. “no threshold voltages of electronic valve devices” has been replaced with “no
voltage drop in the assemblies.]
3.1.5
real no-load direct voltage
U
d00
actual mean direct voltage at zero direct current
[SOURCE: IEC 60050-551:1998, 551-17-19]
3.1.6
ideal crest no-load voltage
U
iM
crest value of the voltage, appearing between the end terminals of an arm neglecting internal
and external voltage surge and voltage drops in valves, at no load
3.1.7
inherent voltage drop
direct voltage drop related to the ideal no load voltage excluding the effect of the 3AC system
impedance
3.1.8
transition current
mean direct current of a converter connection when the direct current(s) of the commutation
group(s) become(s) intermittent when decreasing the current
[SOURCE: IEC 60050-551:1998, 551-17-20]
3.1.9
leakage reactance of the primary winding
X
P
difference between the mean of the short-circuit reactance
values measured between the primary winding and each secondary winding and one half of the
short-circuit reactance measured between the two secondary windings
3.1.10
leakage reactance of each of the secondary windings
X , X
S1 S2
sum of the half difference of the short-circuit reactance values
measured between the primary winding and each secondary winding and one half of the short-
circuit reactance measured between the two secondary windings
IEC 62590-2-1:2025 © IEC 2025
3.1.11
reactance ratio
coupling factor
K
ratio between the leakage reactance of the primary winding
and the sum of the leakage reactances of the primary winding and secondary winding
Note 1 to entry: In case of a traction transformer with two secondary windings, used for a twelve-pulse converter,
the reactance ratio is designed to have the same no-load secondary voltages and the same impedance between the
primary winding and each secondary winding, in order to obtain an even sharing of the current on both bridges in
case the DC outputs are paralleled. Then X = X = X and K = X / (X + X ).
S1 S2 S p S p
3.1.12
interphase transformer
electromagnetic device enabling the operation in parallel of two or more phase displaced
commutating groups through inductive coupling between the windings placed on the same core
[SOURCE: IEC 60050-551:1998, 551-14-16]
3.1.13
rated 3AC voltage
rated voltage of the rectifier on the 3AC power network side
3.1.14
rated 3AC voltage of a rectifier diode assembly
highest value of the transformer traction side no-load voltage that a rectifier diode assembly is
designed for
3.1.15
rated current
rated load
I
Nd
value of a DC current that a rectifier is designed for
Note 1 to entry: All rated values of the components are derived from this value.
Note 2 to entry: A rectifier can have a rated continuous load and rated currents in conjunction with a duty class.
3.1.16
rated power
rated direct current multiplied by DC voltage at rated current
3.1.17
rated AC short-circuit current
short-circuit withstand current on the AC side of a rectifier diode
assembly for every 3AC connection
Note 1 to entry: For a twelve-pulse connection the rated short-circuit current is applicable for each individual six-
pulse diode assembly.
Note 2 to entry: It is an initial short-circuit current according to IEC 60909-0.
3.1.18
rated DC short-circuit current
short-circuit withstand current on the DC side of a rectifier diode
assembly
IEC 62590-2-1:2025 © IEC 2025
3.2 Symbols
d resistive direct voltage drop of the rectifier related to U at rated current
rN di
d inductive direct voltage drop of the rectifier related to U at rated current
xN di
f frequency of the 3AC power network
N
I direct current
d
I maximum current value of the range of linear voltage drop
dlinmax
I rated DC current on the traction side of the rectifier
Nd
I transformer phase current on the valve side
v
K coupling factor
p number of pulses
U real no-load direct voltage, theoretically resulting from peak value of a symmetrical
d00
sinusoidal 3AC voltage U
v0
U ideal no-load direct voltage
di
U ideal crest no-load voltage
iM
u impedance voltage of the transformer
kt
u , u impedance voltage of a three-winding transformer with one secondary winding
kt1 kt2
shorted for winding 1 (u ) or winding 2 (u )
kt1 kt2
U DC voltage at rated DC current in V
Nd
U no-load phase to phase voltage of the transformer valve side
v0
X leakage reactance of the primary winding (for three-winding transformer)
P
X mean value of the leakage reactance of each of the secondary windings (for three-
S
winding transformer)
X X leakage reactance of each of the secondary windings (for transformer with two
S1 S2
secondary windings)
X short-circuit reactance between the primary winding and secondary winding 1
scP/S1
(for transformer with two secondary windings)
X short-circuit reactance between the primary winding and secondary winding 2
scP/S2
(for transformer with two secondary windings)
X short-circuit reactance between both secondary windings (for transformer with two
scS1/S2
secondary windings)
X short-circuit reactance between the primary winding and both secondary windings
scP/S1S2
(for transformer with two secondary windings)
3.3 Abbreviated terms
3AC three phase AC
AC alternating current
DC direct current
RMS root mean square
IEC 62590-2-1:2025 © IEC 2025
4 System configurations and characteristics
4.1 General
DC railway systems are normally fed by a 3AC power network via a rectifier, see Figure 1.

Figure 1 – General configuration
Diode rectifiers allow for a power flow from 3AC power network to the DC traction system only.
The voltage versus current characteristic is determined by the connection and the transformer
main data.
Rectifier diode assemblies and their transformers can be specified separately if a few
parameters are clear:
– load conditions for the transformer and rectifier diode assembly;
– short-circuit withstand of the rectifier diode assembly;
– short-circuit current limited by the transformer;
– maximum U valve side no-load voltage of transformer.
v0
The optional interphase transformer for connection 9 is considered to be part of the rectifier
diode assembly.
Protection at 3AC power network side is normally realized by a circuit breaker and a dedicated
protection relay. In rare cases a combination of load break switch and fuse can be used.
Protection on the DC side is ensured by DC switchgear according to the IEC 61992 series.
4.2 Main interfaces
The interface to the 3AC power network is characterized by:
– rated voltage of the 3AC power network;
– short-circuit power of the 3AC power network;
– voltage imbalance of the 3AC power network;
– harmonic predistortion of the 3AC power network;
– current harmonics by the rectification.
A method to determine the power factor at the 3AC connection of the rectifier is described in
Annex B.
IEC 62590-2-1:2025 © IEC 2025
The interface to the DC traction network is characterized by:
– voltage characteristic of the rectifier;
– voltage harmonics by the rectification.
4.3 Transformer main values
4.3.1 General
A rectifier transformer is characterized by the following main values:
– 3AC power network voltage;
– traction side no-load voltage;
– impedance voltages;
– coupling factor.
The traction side no-load voltage is a main value for calculation of all other voltages.
The impedance voltage is only one value for two-winding transformers. For three-winding
transformers there is more than one value for the impedance voltage.
For a complete transformer specification, other values are necessary. IEC 62695 shall be used.
4.3.2 Impedance voltages
The impedance voltage can be derived from short-circuit tests of the transformer. It can also be
expressed as an impedance. For practical purpose the reactance is far more important than the
resistance as for the interesting power range the X/R ratio is 8 or higher.
For connection 8 from Table 1, only one reactance is applicable. Only one test is applicable.
For connection 9 and 12 from Table 1 two reactances are applicable, see Figure 2. All of the
following 4 tests are applicable.

Figure 2 – Reactances of a rectifier transformer
The different reactances can be determined by measurements.
Test 1: application of a voltage on primary side and short-circuit on secondary side winding 1
X = X + X is measured. The corresponding impedance voltage is u . For u 50 % of
scP/S1 P S1 kt1 kt1
the transformer power is applicable.
Test 2: application of a voltage on primary side and short-circuit on secondary side winding 2
X = X + X is measured. The corresponding impedance voltage is u . For u 50 % of
scP/S2 P S2 kt2 kt2
the transformer power is applicable.
Both values shall almost be the same. For tolerances IEC 62695 shall apply. Otherwise, the
transformer is not symmetric and a current imbalance between the two secondary windings and
their connected rectifier diode bridges will occur.
IEC 62590-2-1:2025 © IEC 2025
These measured reactances are determining the linear behaviour of the rectifier from low load
to overload.
Test 3: application of a voltage on the primary side and short-circuit on both secondary
windings. X = X + X /2 is measured. The corresponding impedance voltage is u . For
scP/S1S2 P S kt
u the full transformer power is applicable.
kt
This reactance is determining the short-circuit current of the rectifier in connection 9.
Test 4: application of a voltage on secondary side winding 1 and short-circuit on secondary
winding 2 or vice versa. For the resulting impedance voltage 50 % of the transformer power is
applicable.
X = X + X is measured.
scS1/S2 S1 S2
More accurate results are possible taking into account the resistances and the short-circuit
impedance of the feeding 3AC power network. The connection between the transformer and
rectifier diode assembly may have an influence.
With the measured values, the values from the equivalent circuit, see Figure 2, can be
calculated. The measurements are redundant.
XX+ X
scP/S1 scP/S2 scS1/S2
X − (1)
p
XX− X
scP/S1 scP/S2 scS1/S2
(2)
X +
S1
XX− X
scP/S2 scP/S1 scS1/S2
X + (3)
S2
4.3.3 Coupling factor
The definition of the coupling factor in 3.1.11 leads to Formula (4) and Formula (5).
K = X / (X + X )
(4)
P S P
u
kt
K −1
(5)
u
kt1
Solving Formulae (1), (2) and (3), the coupling factor can be calculated.
=
=
=
=
IEC 62590-2-1:2025 © IEC 2025
The coupling factor can be adjusted by the winding arrangement within the transformer. A
closely coupled transformer needs specially integrated low voltage windings and a K around
0,9 is possible. To achieve a low coupling factor two separate transformers can be used or a
split high voltage winding connected in parallel. Without any special measure the coupling factor
can vary in a wide range.
4.4 Electrical connections
Standard design of uncontrolled rectifiers is based on a six-pulse bridge connection. Two or
more six-pulse bridges can be connected in parallel or series to achieve a twelve-pulse or 24-
pulse characteristic.
Every six-pulse bridge requires an own three-phase system on the traction side of the
transformer. A twelve-pulse behaviour is achieved by a phase shift of 30° which is realized by
a star and a delta winding with the same vector group on the 3AC power network side of the
transformer.
Combinations of six-pulse bridges are used to eliminate low order current harmonics on the AC
side and low order voltage harmonics on the DC side.
Twelve-pulse and 24-pulse behaviour can be achieved with this combination including a phase
shift between the transformer windings. For a 24-pulse behaviour, two transformers with a
phase shift of +7,5° and −7,5° are used to achieve a phase shift of total 15°.
Table 1 gives values of calculation factors for the most used connections of uncontrolled
rectifiers. For other connections IEC 60146-1-1 and IEC TR 60146-1-2 assists.
IEC TR 60146-1-2 describes the ideal harmonic behaviour under symmetric and sinusoidal 3AC
network conditions as well as a perfect symmetrical transformer. In practice a current or voltage
imbalance can be expected, and the perfect elimination of the harmonics cannot be achieved.
Current imbalance consequences are described in 4.7.
IEC 62590-2-1:2025 © IEC 2025
Table 1 – Connections and calculation factors for uncontrolled rectifiers
Con- Transformer
U U U
di d00
iM
I /I  d /u d /u
nection connection Valve connection p
v d xN kt1 xN kt
U U U
no. valve side v0 di di
0,816 1,35
1,05 1,05
1      or   1
8 1 2 3 6   0,5 0,5
2 32 π π
 
3   2        2
   
3 π 3 3
 
 
1,35
0,408 1,05
1,05
1          2
a
9 1 3 5 2 4 6 12 0,5
1 32 0,26
  π π
 
5   3        4
    
π
3 3
 6

0,816 2,7
1,05 0,524
1          2
6 a
1 3 5 2 4 6
12 12    0,5 0,26
2 62 π π
 
5   3        4
    
3 π 3 6
 
  
NOTE 1 Connection 9 can be used with or without interphase transformer. For high coupling factors an interphase
transformer is normally used. For low coupling factor no interphase transformer is used except for low transition
current requirements.
NOTE 2 Additionally to preceding standards, d /u is given as it provides a factor independent from the coupling
xN kt1
factor.
NOTE 3 The connection numbers are the same as those used in IEC 60146-1-1.
NOTE 4 The interphase transformer can be arranged in the positive or the negative polarity.
NOTE 5 The real no load voltage U can rise to higher values than indicated due to capacitive effects. In these
d00
cases a base load resistor is commonly used.
a
The factor of 0,26 is given for an ideal coupling. The value is a function of the coupling factor. The range can
have any value between 0,26 and 0,5. Values used in practice are 0,26 and 0,5.

4.5 Voltage characteristic
The typical voltage characteristic with its characteristic values is shown in Figure 3. A method
to determine voltage versus current characteristic for higher currents, is described in Annex A.
The basic value is the transformer no-load voltage on the valve side of the rectifier transformer.
The ideal no-load voltage can be taken from Table 1.
The real no-load voltage is higher than the ideal no-load voltage.
The current at which the waveform changes from intermitting to continuous is called transition
current. The transition current is dependent on the rectifier connection. For connection 8 and
12 from Table 1 it is a few amperes. It depends on the smoothing effect of snubber circuits.
For connection 9 from Table 1 the transition current depends on the coupling factor and the
application of an interphase transformer. The effect of interphase transformers is described in
Annex C.
IEC 62590-2-1:2025 © IEC 2025
There is no general rule for the choice of the transition current value. An intermittent current
increases the resistance borne losses in the rectifier diode assembly and the transformer. This
is not important for low current. The total voltage versus current characteristic may be nonlinear.
There is a negligible effect on 3AC as well as DC harmonics. A value of transition current less
than 30 % of rated current can be considered as a guideline. A special requirement should be
specified by the user.
For a current higher than the transition current the characteristic is linear up to a value where
the current waveshape changes significantly. More details are shown in Annex A. The voltage
drop in the linear range is determined by the impedance voltage measured with one traction
side winding shorted.
du= 0,5
xN kt1
At full short-circuit the current waveshape of the supply phases is almost sinusoidal. The value
of the short-circuit current is determined by the impedance voltage with all traction side windings
shorted.
Figure 3 – Voltage characteristic
4.6 Current characteristic
The quotient of the RMS value I of the current on the AC side and the direct current I is listed
v d
in Table 1 on the assumption of smooth direct current and rectangular waveshape of the
alternating currents.
This precondition is not given for currents lower than the transition current.
At short circuits the AC current is almost sinusoidal.
IEC 62590-2-1:2025 © IEC 2025
4.7 Current i
...