C22.2 No. 66.3-06

(reaffirmed 2020)

Low Voltage Transformers — Part 3: Class 2 and Class 3 Transformers

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Update No. 1

C22.2 No. 66.3-06

November 2012

Note: For information about the Standards Update Service, go to shop.csa.ca or e-mail

techsupport@csagroup.org.

Title: Low Voltage Transformers — Part 3: Class 2 and Class 3 Transformers — originally published April 2006

The following revisions have been formally approved and are marked by a vertical line in the margin on the attached replacement pages:

• Update your copy by inserting these revised pages.

• Keep the pages you remove for reference.

CSA Group

CSA C22.2 No. 66.3-06

First Edition

Underwriters Laboratories Inc. UL 5085-3

First Edition

Low Voltage Transformers – Part 3: Class 2 and Class 3 Transformers

April 17, 2006

(Title Page Reprinted: November 30, 2012)

ANSI/UL 5085-3-2012

Commitment for Amendments

This standard is issued jointly by the Canadian Standards Association (operating as “CSA Group”) and Underwriters Laboratories Inc. (UL). Comments or proposals for revisions on any part of the standard may be submitted to CSA Group or UL at any time. Revisions to this standard will be made only after processing according to the standards development procedures of CSA Group and UL. CSA Group and UL will issue revisions to this standard by means of a new edition or revised or additional pages bearing their date of issue.

ISBN 1-55436-211-3 © 2006 CSA Group

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Copyright © 2012 Underwriters Laboratories Inc.

The most recent designation of ANSI/UL 5085-3 as a Reaffirmed American National Standard (ANS) occurred on November 30, 2012. ANSI approval for a standard does not include the Cover Page, Transmittal Pages, Title Page (front and back), or the Preface.

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CONTENTS

Preface 5

1 Scope 7

4 Construction 7

6 Enclosure 8

6.1 General 8

8 Connections 9

8.2 Wiring terminals 9

8.5 Leads 9

11 Spacings and Insulation 10

1. Insulating material for mounting of low voltage live parts 10

2. Coil insulation 10

11.4 Insulation in lieu of spacings ................................................ .10A

11.5 Spacings .................................................................. .10A

11.6 Separation of internal wiring circuits .......................................... .10A

12 Switches, Protective Devices, and Wiring Devices .................................... .10B 12.3 Protective devices ......................................................... .10B 12.4 Separate current-limiting impedances 12

12.5 Overtemperature protective devices 12

17 Markings 12

17.1 General 12

1. Ratings 12

2. Details 13

18 Tests 14

1. Open Circuit Secondary Voltage Test 15

2. Output Current and Power Test 16

   1. Maximum current output of inherently limited transformers 16

   2. Maximum current of non-inherently limited transformers 17

   3. Maximum power of non-inherently limited transformers 17

3. Calibration Test of Overcurrent Protective Devices 19

4. Rated Secondary Current Test 19

5. Rated Output Heating Test 19

6. Dielectric Voltage-Withstand Test 21

   1. General 21

   2. Induced potential 22

7. Overload Heating Test 22

   1. General 22

   2. Procedure 23

8. Dielectric Voltage-Withstand After Overload Heating Test 24

9. Overload Test of Overcurrent or Overtemperature Protective Devices 24

10. Endurance Test of Automatically Reset Overtemperature Protective Devices 24

11. Strain Relief Test 25

Annex A (Informative)

A1 Production Line Dielectric Voltage Withstand Test 31

Annex C (Informative)

C1 French Translations of Markings 32

Annex D (Normative)

D1 Class 3 Transformers 33

D1.1 General 33

D1.2 Marking 33

D1.3 Tests 34

D1.4 Leakage current test 36

Preface

This is the harmonized CSA Group and UL standard for low voltage transformers. It is the first edition of CSA C22.2 No. 66.3 and the first edition of UL 5085-3. This harmonized standard has been jointly revised on November 30, 2012. For this purpose, CSA Group and UL are issuing revision pages dated November 30, 2012.

This harmonized standard was prepared by a Technical Harmonization Committee comprised of members from CSA Group, Underwriters Laboratories Inc. (UL), and representatives of the low voltage transformer manufacturing industry. The efforts and support of the members of the Technical Harmonization Committee are gratefully acknowledged.

This Standard is considered suitable for use for conformity assessment within the stated scope of the Standard.

This standard was reviewed by the CSA Subcommittee on C22.2 No. 66, under the jurisdiction of the CSA Technical Committee on Industrial Products and the CSA Strategic Steering Committee on Requirements for Electrical Safety, and has been formally approved by the CSA Technical Committee.

This Standard has been approved by the American National Standards Institute (ANSI) as an American National Standard.

Where reference is made to a specific number of samples to be tested, the specified number is to be considered a minimum quantity.

Note: Although the intended primary application of this standard is stated in its scope, it is important to note that it remains the responsibility of the users of the standard to judge its suitability for their particular purpose.

Level of harmonization

This standard uses the IEC format but is not based on, nor is it to be considered equivalent to, an IEC standard. This standard is published as an equivalent standard for CSA Group and UL.

An equivalent standard is a standard that is substantially the same in technical content, except as follows: Technical national differences are allowed for codes and governmental regulations as well as those recognized as being in accordance with NAFTA Article 905, for example, because of fundamental climatic, geographical, technological, or infrastructural factors, scientific justification, or the level of protection that the country considers appropriate. Presentation is word for word except for editorial changes.

Reasons for Differences from IEC

The Technical Harmonization Committee identified the following IEC Standard within the scope of this standard: IEC 61558-1 (1998-07), Safety of power transformers, power supply units, and similar - Part 1: General requirements.

The THC determined that the safe use of transformers and reactors is critically dependent on the electrical system in which they are intended to be installed. Significant investigation is required to assess safety and system compatibility issues that may lead to harmonization of traditional North American transformers and reactors with those presently addressed in the known IEC standards. The THC agreed such future investigation might be facilitated by completion of harmonization of North American standards for transformers and reactors.

Interpretations

The interpretation by the standards development organization of an identical or equivalent standard is based on the literal text to determine compliance with the standard in accordance with the procedural rules of the standards development organization. If more than one literal interpretation has been identified, a revision is to be proposed as soon as possible to each of the standards development organizations to more accurately reflect the intent.

CSA Group Effective Date

The effective date for CSA Group will be announced through CSA Informs or a CSA Group certification notice.

UL Effective Date

This Standard is now in effect.

Parts

The Standard for Low Voltage Transformers is divided into the following parts:

PART 3: CLASS 2 AND CLASS 3 TRANSFORMERS

1 Scope

1.1 As noted in Low Voltage Transformers – Part 1: General Requirements, UL 5085-1, or CSA C22.2 No. 66.1, Low Voltage Transformers – Part 1: General Requirements, the requirements in Part 3 cover Class 2 transformers for use with Class 2 circuits in accordance with the National Electrical Code, ANSI/NFPA 70, or the Canadian Electrical Code, Part I, CSA C22.1. They are intended for connection to essentially sinusoidal supply sources.

Advisory Note: For transformers intended for use in the United States, these requirements also cover Class 3 transformers for use with Class 3 circuits in accordance with the National Electrical Code, ANSI/NFPA 70, unless otherwise specified in this standard. See Annex D for Class 3 requirements.

1. In addition to the items specified in Clause 1.3 of Part 1, the requirements of Part 3 do not cover:

   
   

   1. Power supplies (a transformer provided with a rectifier is considered a power supply);

      
      

   2. Toy transformers;

      
      

   3. Cord and plug connected transformers other than Class 3;

      
      

   4. Direct plug-in transformers;

      
      

   5. Transformers intended for use in audio, radio, or television type appliances; or

      
      

   6. Other special types of transformers covered in requirements for other electrical devices or appliances.

Advisory Note: The requirements of Part 3 do not cover transformers intended for use in the United States having a nominal primary rating of more than 600 V and transformers having overvoltage taps rated over 660 V.

1. This part is intended to be used in conjunction with Part 1. The numbering of the clauses in Part 3 corresponds to the numbered clauses in Part 1. The requirements in Part 1 apply unless modified by Part 3.

   
   

2. A Class 2 transformer that includes a separate current-limiting impedance such as a resistor or a positive temperature coefficient device (PTC) is covered by these requirements.

   
   

3. A Class 2 transformer that includes a resonance regulating circuit is covered by these requirements.

4 Construction

4.2 A Class 2 transformer shall have only one secondary winding, which shall be insulated from the primary winding. A winding having intermediate taps is considered a single winding.

Note 1: Two or more secondary windings may be considered as a single winding and interposing insulation between the secondary windings is not required if the windings, when interconnected, are in compliance with the performance requirements for a single-winding construction.