UL 551:8ED 2009-04

Foreword
Introduction
1 Scope
2 Components
3 Units of measurement
4 References
5 Terminology
Construction
6 General
7 Frame and enclosure
8 Accessibility of live parts
9 Protection against corrosion
10 Supply connections
11 Wire-bending space
12 Grounding
13 Spacings
14 Mechanical assembly
15 Internal wiring
16 Current-carrying parts
17 Electrical insulating materials
18 Capacitors
19 Fans
20 Overload protection
21 Receptacles
22 Switches and control devices
23 Transformers
Performance
24 General
25 Leakage current test
26 Leakage current test following humidity conditioning
27 Output test
28 Input test
29 Short-circuit current test
30 Temperature test
31 Dielectric voltage-withstand test
32 Overload test on switches and controls
33 Endurance test on switches and controls
34 Dielectric voltage-withstand test on switches and
    controls
35 Short circuit test on capacitors
36 Abnormal operation test
37 Stalled fan abnormal operation test
38 Compression and torsion test
39 Strain relief test
40 Permanence of marking
Manufacturing and production tests
41 Grounding continuity
Rating
42 Details
Marking
43 Details
Instructions
44 Instruction manual
Appendix
A Standards for components

This revision to UL 551 is being issued to reaffirm the Eighth Edition of the Standard for Safety for Transformer-Type Arc-Welding Machines, UL 551, as an American National Standard and to incorporate an editorial correction to the Table of Contents.

These requirements cover limited duty welding and cutting power sources, wire feeders, torches, and electrode holders that are intended for use by a layperson in a nonindustrial setting in accordance with the National Electrical Code, NFPA 70.