C22.2 NO. 66.3-06 (R2025)

Description

Preface This is the common CSA 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 edition of CSA C22.2 No. 66.3 supersedes the requirements of CSA C22.2 No. 66 published in 1988. This edition of UL 5085-3 supersedes the Fourth edition of UL 1585 published in 1998. This common standard was prepared by a Technical Harmonization Committee comprised of members from the Canadian Standards Association (CSA), 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 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. 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. 1.3 In addition to the items specified in Clause 1.3 of Part 1, the requirements of Part 3 do not cover: a) Power supplies (a transformer provided with a rectifier is considered a power supply); b) Toy transformers; c) Cord and plug connected transformers; d) Direct plug-in transformers; e) Transformers intended for use in audio, radio, or television type appliances; or f) 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. 1.7 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. 1.8 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. 1.9 A Class 2 transformer that includes a resonance regulating circuit is covered by these requirements.