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. 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. 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. 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. A Class 2 transformer that includes a resonance regulating circuit is covered by these requirements.
UL 5085-3-2006 history
1970UL 5085-3-2022 Low voltage transformers - Part 3: Class 2 and Class 3 transformers
2017UL 5085-3 BULLETIN-2017 UL Standard for Safety Low Voltage Transformers - Part 3: Class 2 and Class 3 Transformers (COMMENTS DUE: November 27@ 2017)
2012UL 5085-3 BULLETIN-2012 UL Standard for Safety Low Voltage Transformers - Part 3: Class 2 and Class 3 Transformers (COMMENTS DUE: August 13@ 2012)
2011UL 5085-3 BULLETIN-2011 UL Standard for Safety Low Voltage Transformers - Part 3: Class 2 and Class 3 Transformers (COMMENTS DUE: July 05@ 2011)
2010UL 5085-3 CRD-2010 UL Standard for Safety Low Voltage Transformers - Part 3: Class 2 and Class 3 Transformers - Section / Paragraph Reference: Table 7 Subject: Maximum temperature rise for Class 120(E) transformer insulation system (Edition 1: April 17, 2006)
2007UL 5085-3 BULLETIN-2007 UL Standard for Safety Standard Low Voltage Transformers - Part 3: Class 2 and Class 3 Transformers
2006UL 5085-3 BULLETIN-2006 UL Standard for Safety Standard Low Voltage Transformers - Part 3: Class 2 and Class 3 Transformers
2006UL 5085-3-2006 Low voltage transformers - Part 3: Class 2 and Class 3 transformers