EN IEC 60034-26:2026

Rotating electrical machines - Part 26: Effects of unbalanced voltages on the performance of three-phase cage induction motors

IEC 60034-26:2026 is available as IEC 60034-26:2026 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 60034-26:2026 describes the effects of unbalanced voltages on the performance of three-phase cage induction motors. This second edition cancels and replaces the first edition published in 2006. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) clarification that voltages are line-to-line voltages in Clause 4, Annex A and Annex B; b) addition of design NE according to IEC 60034-12 in Clause 4.

Drehende elektrische Maschinen - Teil 26: Auswirkungen von Spannungsunsymmetrien auf das Betriebsverhalten von Drehstrom-Induktionsmotoren

Machines électriques tournantes - Partie 26: Effets d'un système de tensions déséquilibrées sur les caractéristiques de fonctionnement des moteurs à induction à cage triphasés

IEC 60034-26:2026 est disponible sous forme de IEC 60034-26:2026 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.IEC 60034-26: 2026 décrit les effets des tensions déséquilibrées sur les caractéristiques de fonctionnement des moteurs à induction à cage triphasés. Cette deuxième édition annule et remplace la première édition parue en 2006. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: a) clarification indiquant que ces tensions sont des tensions entre phases à l’Article 4, à l’Annexe A et à l’Annexe B; b) ajout de la conception NE conformément à l'IEC 60034-12 à l’Article 4.

Električni rotacijski stroji - 26. del: Vpliv nesimetričnih napetosti na lastnosti trifaznih motorjev s kratkostično kletko (IEC 60034-26:2026)

General Information

• Status: Published
• Publication Date: 26-Feb-2026
• ICS: 29.160.01 - Rotating machinery in general
• Technical Committee: CLC/TC 2 - Rotating machinery
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 27-Feb-2026
• Due Date: 02-Feb-2026
• Completion Date: 27-Feb-2026
• Ref Project: SIST EN IEC 60034-26:2026 - Rotating electrical machines - Part 26: Effects of unbalanced voltages on the performance of three-phase cage induction motors (IEC 60034-26:2026)

Relations

• Replaces: EN 60034-26:2006/AC:2014 - Rotating electrical machines - Part 26: Effects of unbalanced voltages on the performance of three-phase cage induction motors
• Effective Date: 09-Jul-2024
• Replaces: EN 60034-26:2006 - Rotating electrical machines - Part 26: Effects of unbalanced voltages on the performance of three-phase cage induction motors
• Effective Date: 09-Jul-2024
• Referred By: EN IEC 60034-23:2019 - Rotating electrical machines - Part 23: Repair, overhaul and reclamation
• Effective Date: 03-Mar-2026
• Referred By: EN 50549-10:2022 - Requirements for generating plants to be connected in parallel with distribution networks - Part 10: Tests for conformity assessment of generating units
• Effective Date: 03-Mar-2026

Overview

EN IEC 60034-26:2026 – “Rotating electrical machines – Part 26: Effects of unbalanced voltages on the performance of three-phase cage induction motors” – is an international standard developed by the International Electrotechnical Commission (IEC), maintained within Europe by CLC. This second edition replaces the first edition from 2006 and introduces critical revisions, notably clarifying voltage definitions and expanding coverage to include design NE motors as per IEC 60034-12.

This standard is essential for manufacturers, plant engineers, operators, and maintenance teams working with three-phase cage induction motors, focusing on how unbalanced supply voltages impact electrical, thermal, and mechanical performance. Understanding these effects helps ensure the safety, reliability, and efficient operation of rotating electrical machines in industrial and infrastructure applications.

Key Topics

• Unbalanced Voltages: Defines unbalanced voltage as a deviation in the symmetry of a three-phase system, leading to significant operational issues in electric motors.
• Impact on Motor Performance: Details how voltage unbalance affects key performance parameters:
  • Currents: Small voltage unbalances result in disproportionately high current unbalance, increasing losses and heating.
  • Heating: Negative-sequence currents elevate winding temperatures, raising the risk of insulation damage.
  • Torque: Reduction in locked-rotor, pull-up, and breakdown torque, potentially causing inadequate torque for applications and introducing oscillating torques.
  • Speed and Efficiency: Full-load speed slightly reduced; overall efficiency may decrease due to additional losses.
• Derating Guidance: Provides factors and recommendations for derating motor power output where the negative-sequence voltage exceeds 1% of the positive sequence component, helping prevent overheating and ensuring reliable service.
• Calculation Methods: Outlines graphical, analytical, and approximate methods for determining the degree of voltage unbalance and its impact, with practical formulas and diagrams included in the annexes.

Applications

EN IEC 60034-26:2026 is critical in sectors where three-phase cage induction motors are widely used, such as:

• Industrial Plants: Ensuring motors run efficiently under varied grid conditions and avoiding unexpected downtime due to voltage unbalance.
• Utilities and Power Distribution: Assessing the impact of supply disturbances on motor-driven systems, facilitating corrective measures in grid management.
• Infrastructure Projects: Reliable operation of ventilation, water pumps, and HVAC systems where supply quality can fluctuate.
• Motor Manufacturers and OEMs: Designing and specifying electric motors that can withstand supply asymmetries, and providing accurate application guidelines to end users.
• Maintenance and System Engineers: Implementing monitoring and derating strategies to prevent failures and extend motor life when operating under non-ideal voltage conditions.

Related Standards

For comprehensive system design and compliance, EN IEC 60034-26:2026 should be used together with other key standards:

• IEC 60034-12: Covers starting performance of single-speed three-phase cage induction motors, referenced for design types N and NE in derating context.
• IEC 60034 Series: General specifications and testing methods for rotating electrical machines, offering holistic guidance for machine design and operation.
• IEC Directives, Part 2: Procedures and drafting conventions for international electrotechnical standards, ensuring consistency across documents.
• Other Grid Quality Standards: For broader power quality assessment, including voltage disturbance and harmonic standards.

EN IEC 60034-26:2026 helps ensure the safe, reliable, and efficient operation of three-phase cage induction motors exposed to unbalanced supply voltages by providing clear definitions, calculation methods, and practical application guidance. This is vital for meeting regulatory requirements, minimizing operational risks, and optimizing performance in demanding environments.

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN IEC 60034-26:2025
01-april-2025
Električni rotacijski stroji - 26. del: Učinki napetostnih neravnovesij na delovanje
trifaznih indukcijskih motorjev s kletko
Rotating electrical machines - Part 26: Effects of unbalanced voltages on the
performance of three-phase cage induction motors
Drehende elektrische Maschinen - Teil 26: Auswirkungen von Spannungsunsymmetrien
auf das Betriebsverhalten von Drehstrom-Induktionsmotoren
Machines électriques tournantes - Partie 26: Effets d'un système de tensions
déséquilibrées sur les caractéristiques de fonctionnement des moteurs à induction à
cage triphasés
Ta slovenski standard je istoveten z: prEN IEC 60034-26:2025
ICS:
29.160.30 Motorji Motors
oSIST prEN IEC 60034-26:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN IEC 60034-26:2025
oSIST prEN IEC 60034-26:2025
2/2224/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60034-26 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2025-01-31 2025-04-25
SUPERSEDES DOCUMENTS:
2/2203/CD, 2/2220/CC
IEC TC 2 : ROTATING MACHINERY
SECRETARIAT: SECRETARY:
United Kingdom Mr Charles Whitlock
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
SC 121A
ASPECTS CONCERNED:
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of
which they are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some
Countries” clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is the
final stage for submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Rotating electrical machines - Part 26: Effects of unbalanced voltages on the performance of
three-phase cage induction motors

PROPOSED STABILITY DATE: 2027
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
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oSIST prEN IEC 60034-26:2025
IEC CDV 60034-26 ED2 © IEC 2024 2 2/2224/CDV
1 CONTENTS
2 FOREWORD . 3
3 INTRODUCTION . 5
4 1 Scope . 6
5 2 Normative references . 6
6 3 Effects of unbalanced voltages on performance . 6
7 3.1 Currents . 6
8 3.2 Heating . 6
9 3.3 Torque . 7
10 3.4 Full-load speed . 7
11 4 Derating of motor to prevent overheating . 7
12 Annex A (informative) Determination of the symmetrical components of the line-to-line
13 voltages U , U , U of a three-phase system . 9
1 2 3
14 A.1 Graphical determination . 9
15 A.2 Analytical determination . 10
16 Annex B (informative) Approximate determination . 11
18 Figure 1 – Typical values of derating of design N or NE, three-phase cage induction
19 motors within the scope of IEC 60034-12 . 8
20 Figure A.1 – Phasor diagram . 9
oSIST prEN IEC 60034-26:2025
IEC CDV 60034-26 ED2 © IEC 2024 3 2/2224/CDV
23 INTERNATIONAL ELECTROTECHNICAL COMMISSION
24 ____________
26 ROTATING ELECTRICAL MACHINES –
28 Part 26: Effects of unbalanced voltages on the performance
29 of three-phase cage induction motors
32 FOREWORD
33 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
34 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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64 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
65 patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
66 International Standard IEC 60034-26 has been prepared by IEC technical committee 2:
67 Rotating machinery.
68 This standard cancels and replaces IEC 60034-26 ed. 1 published in 2006. This edition
69 constitutes a technical revision.
70 This edition includes the following significant technical changes with respect to the previous
71 edition:
Clause or
Change
subclause
4, Annexes Clarification that voltages are line-to-line voltages
4 Design NE according to IEC 60034-12 added
73 The text of this standard is based on the following documents:

oSIST prEN IEC 60034-26:2025
IEC CDV 60034-26 ED2 © IEC 2024 4 2/2224/CDV
FDIS Report on voting
75 Full information on the voting for the approval of this standard can be found in the report on
76 voting indicated in the above table.
77 This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
78 A list of all parts of IEC 60034 series, under the general title Rotating electrical machines can be found
79 on the IEC website.
80 The committee has decided that the contents of this publication will remain unchanged until
81 the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
82 the data related to the specific publication. At this date, the publication will be
83 • reconfirmed,
84 • withdrawn,
85 • replaced by a revised edition, or
86 • amended.
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