UL 551:2009 free download

UL 551:2009 free download Transformer-Type Arc-Welding Machines
4References
4.1 Any undated reference to a code or standard appearing in the requirements of this standard shall beinterpreted as referring to the latest edition of that code or standard.
5 Terminology
5.1 ln the following text, a requirement that applies only to a particular type of product is so identified bya specific reference in that requirement to the type or types of products involved. Absence of such specificreference or use of the term product indicates that the requirement applies to all types of products unlessthe context indicates otherwise.
cONSTRUCTION
6 General
6.1 An enclosure, an opening, a frame, a guard, a knob, a handle, or the like shall not be sutficiently sharpto cause a risk of injury to persons during normal maintenance or use.
Exception: A sharp edge that must be exposed to enable the product to perform its intended function.6.2 A welding lead or electrode holder that is attached to a product shall be acceptable for the purpose.7 Frame and Enclosure
7.1 A product shall be formed and assembled so that it will have the strength and rigidity necessary toresist the abuses to which it may be subjected, without increasing the risk of fire, electric shock, or injuryto persons due to total or partial collapse with resulting reduction of spacings, loosening or displacementof parts, or other serious defects.
7.2 A product shall be provided with a case or cabinet that encloses all live parts.
Exception No.1 : A flexible supply cord or cable and welding leads need not be enclosed.
Exception No. 2: Ungrounded secondary output terminals for the connection of welding leads, tap jacks,or similar parts connected to the secondary circuit need not be enclosed if they are:
a) Limited in voltage as specified in 27.1.1 ; and
b) Protected so as to reduce the risk of unintentional contact.
7.3 The protection referred to in Exception No.2 to 7.2 will usually be afforded if:
a) Jacks are of the dead-front type,
b) An uninsulated live part is recessed for a distance not less than half the minimum dimensionof the opening behind which the live part is located,
c) A hinged cover is provided over the terminals with smooth-edged slots or openings for thecable, or
7.4 An enclosure shall be made of cast metal, iron, steel, aluminum, copper, or brass.
Exception: Other material that has been investigated and found to be acceptable for the purpose may be used.
7.5 Among the factors to consider in determining the acceptability of an enclosure are its:
a) Mechanical strength,
b) Resistance to impact,
c) Moisture-absorptive properties,
d) Combustibility,
e) Resistance to corrosion,
f) Resistance to distortion at temperatures to which the enclosure may be subjected under
conditions of normal or abnormal use, and
g) Resistance to ignition from electrical sources.
For a nonmetallic enclosure, all of these factors are considered with respect to thermal aging.
7.6 The thickness of a cast-metal enclosure shall be as specified in Table 7.1 .