More Information on Cable
There are times when a power cord or cord set is not readily available for a given application. The plug may be unavailable in a molded configuration. There may be times when the designer or manufacturer would prefer to wait until just prior to shipping to install a plug on the equipment. If the equipment requires more than 3.0–3.5 KVA (kilovolts), or is using three-phase power, a molded-on plug/socket system may not be available. When one of these cases exists, it may be preferable to simply order the required cable.
While there are some commonalities between North American and international cable, there are also some important differences. A discussion of these issues will help the designers clarify their choices.
North American cable specified by the number and gauge of conductors. The gauge uses an inverse relationship to the size, so the larger the number, the smaller the cable. For example, a small gauge North American cable with three conductors might be 3 x 18AWG (American Wire Gauge). This may also be expressed as 18/3AWG. A cable sized 3 x 10 (10/3) would be larger, despite the smaller number.
Cable for single phase applications will either be a 2 wire or 3 wire variety. Cable with 2 wires is for Class II (ungrounded) applications, while 3 wire cable is for Class I applications, which require a ground. Three phase applications are going to require either 4 or 5 wires. Cables with 2 or 3 wires come in two distinct shapes: round or flat. Round cables will have conductors that are insulated separately, inside an outer sheath, which we will discuss later in this article. The conductors will be twisted in a helical pattern throughout the length of the cable. Flat cables will have an entirely different structure, making them noticeably different from round cable. Flat cable will be constructed with conductors that are laid in a parallel fashion. A common example would be SPT type cable. With this type of cable, the line and neutral will not have individual insulation around them of a special color. Instead, the outer jacket acts as the only insulative barrier. Neutral is distinguishable from the line either by a white strip on the outer jacket on one side, or by a series of molded ridges running the entire length of the cable down one side. In a 3 wire version, the ground will have its own internal jacket of either a green or yellow/green color.
The size designation of North American cable is followed by a series of letters, and possibly numbers, such as “SJT”, “SPT-1″ or “SOW.” These letters indicate the characteristics of the cable, such as the jacket type, water/chemical resistance, and abrasion resistance.
These designations are stamped on the exterior jacket for quick and easy reference for the end user, along with the pertinent UL/CSA references, as listed under UL 62 and CSA 49.
The outer jacket on North American cable is typically PVC, thermoplastic, or rubber. Each jacket type offers advantages and disadvantages to the end user. Thermoplastic cable is usually more cost effective than rubber, as well as lighter weight. This makes it an attractive choice for use with items such as household appliances. Rubber cable can be more costly, but does have its advantages. Rubber tends to be more durable, with high levels of water and abrasion resistance. These factors make it an attractive choice for outdoor applications. However, some newer types of thermoplastic cable, such as Interpower flexible North American cable, also exhibit some of these characteristics. The wise designer would do well to carefully review his requirements against some of the newer cable types before making a final selection.
Round North American cable is often manufactured with jute or paper filler. This filler acts to make the cable stronger and enhances the round shape during the extruding process. However, it also makes the cable more labor intensive to deal with when assembling on it, as the filler must be stripped and trimmed away. For this reason, fillerless cable is now often the cable of choice for equipment designers. The fillerless cable will require less preparation and is also somewhat smaller than filled cable. The additional space savings can prove significant in designs where space is limited. In order for Interpower 3 x 18AWG cable to meet the tensile requirements, a strand of Kevlar™ is run down the length of the cable inside the ground wire in place of the filler. All other sizes of Interpower fillerless cable contain no Kevlar™ or filler of any kind.
The inner conductors for round North American cable have either thermoplastic or rubber jackets, in accordance with the outer jacket. For single-phase cable, the conductor color coding is typically: line (black or brown), neutral (white or light blue) and ground (green or green/yellow). Each conductor is sized in accordance with the AWG system.
International cable is similar in appearance to North American cable, but there are a number of important differences. International cable is sometimes referred to as “harmonized,” or simply “HAR.” This comes from the European standards to which the cable is constructed: CENELEC publications HD-21 and HD-22. “HD” (Harmonized document), which is the European Union’s effort to provide consistency in manufacturing cable in Europe. HD-21 is the standard for PVC-jacket cable and HD-22 is the standard for rubber cable. Cable manufactured outside Europe cannot exhibit the “HAR” marking. In this case the cable must be manufactured to the IEC standards for cable: IEC 60227 for PVC jacketed cable and IEC 60245 for rubber jacketed cable. As is the case for North American cable, each jacket type offers advantages and disadvantages.
Harmonized and international cable is measured in square millimeters. This measurement comes from the cross section diameter measurement of each conductor. Hence, the size is expressed as mm2, such as 1.5mm2. Size increments are typically noted every half-millimeter, but this is not required. Some countries like Japan and China have different sizing structures than most other countries. Because the standards and methods of measuring are different, harmonized cable sizes do not correspond with North American sizes. It is also worth noting that harmonized cable does not have filler. Harmonized cable does not have as high a tensile strength as a similar North American cable.
Like North American cable, the inner conductors of harmonized cable are made of material consistent with the outer jacket. All harmonized cable will be color-coded line (brown), neutral (light blue) and ground (yellow/green striped). These conductors are sized with the mm2 measurement.
The property designations for harmonized cable are also quite different from North American cable. See our chart on International “Harmonized” Cable Recommendations. A series of numbers and letters will indicate the jacket material, ratings, and size of the cable. These markings may be found on the outer jacket. However, unlike North American UL markings on cable, the “HD” designators are not always located on the outer jacket of the cable. Harmonized cable standards allow for an inner conductor jacket to display the markings, or a simple colored thread to run throughout the length of the cable. This thread only identifies the cable manufacturer. It does not provide any structural information.
Interpower carries both North American and international shielded cable. Shielded cable is similar to unshielded cable in its manufacture, except it has an added aluminum “shield” that runs the length of the cable. In North American cable, the shield is commonly in a sheet form (foil), with an aluminum drain wire. It sometimes comes in a braided wire mesh method. International cable comes only as the braided wire mesh configuration.
The aluminum acts to pick up stray electrical charges, usually from “bleeding off” within the cable, where the charge may cause interference. Commonly, the aluminum is attached to the ground of the cable to facilitate dispersal of the stray charge. It is important to note that international standards do not call for, nor do they recognize shielded cable. The cable may be built to harmonized standards, but it will not carry any approvals. North American shielded cable, on the other hand, will carry UL and CSA approvals.
For most products and most designs, single-phase cable is all that is required. It is called single-phase due to having only one line conductor. However, some projects may require multi-phase cable.
Multi-phase cable is similar in construction to single-phase, but it will have additional line conductors. Most common is three-phase cable. Three-phase cable has five conductors, in a three-line, one-neutral and one-ground set up. The neutral may sometimes act as a second ground. Interpower carries four-conductor cable, which is similar to three-phase cable, with a ground and three line conductors. These types of cable are usually application specific, used in designs that require higher levels of electricity.
Multi-phase cable will be manufactured to the same specifications as single-phase cable and subject to the same standards. Interestingly, in the past international cable added extra leads in a black color, regardless of whether one or two more conductors were being added. However, cable standards in Europe have been changed to implement a uniform conductor color code (HD 308 52). By April 1, 2006, all cable must be converted to the new system in which one of the black conductors will be replaced with a gray conductor to better distinguish the line conductors. For North American cable, the first extra conductor is red and the second is orange. It is also worth noting that UL and CSA do not test cable larger than 10AWG. The applications for 8 gauge and larger cable become user specific, because of its sheer size and capacity.
As was noted earlier, Interpower now offers cables that offer alternatives to standard rubber. One type is TPE (Thermoplastic Elastomer). TPE offers a very flexible plastic jacket that can withstand extreme cold. Additionally, it is ultra-violet resistant, abrasion resistant, and withstands most chemicals. These features make it an attractive choice for cable that will be exposed to the elements.
Another thermoplastic cable that may suit the designer’s need is oil resistant cable rated at 600V. The oil resistant rating includes most petroleum-based products. This cable offers good abrasion resistance, as the jacket is rated for heavy-duty use.
Interpower is well equipped to provide cable packaged to your company’s specifications. We maintain a large inventory of most of the cable described in this catalog. We can deliver your order on spools in quantities that you specify. We can also deliver cable cut to length so that you eliminate scrap. This service is well suited with large cables that are expensive and difficult to handle.
Interpower uses stripping equipment that makes it easy to strip all of the cables listed in this section. Our striping machines strip conductors up to 50cm. We can also cut and strip conductors to specified lengths and apply crimp terminations which one can specify from a wide variety that we maintain in stock. Standard stock terminations include: ultrasonic weld, ring terminals, spade terminals, straight-style disconnects, flag-style quick disconnects, and ferrules. Our cable stripping and crimp termination services are particularly attractive with large rubber jacketed cable that is difficult to strip and handle.
Interpower can make your complete power cable assemblies by terminating the cable with any of the following: straight blade or locking type plugs and connectors, international plugs and connectors, IEC 60309 high power pin and sleeve devices, IEC 60320 connectors, and related devices.
Our skilled assemblers work in a well-equipped, comfortable manufacturing facility that is ISO 9001 Certified. Continuous training enables our assemblers to perform the wide variety of work that moves through our shop. This assures a quick turnaround time and cable assemblies that will meet your specifications. Assuming that appropriate materials are specified, our power cable assemblies are UL recognized or listed and CSA certified.
Please note that although we can use components certified by agencies other than UL and CSA, complete cable assemblies must be submitted to the agency with the equipment for testing. They will be given an applications approval at that time. This reflects the fact that other agencies use a more restrictive approval process for rewireable power cable assemblies than UL and CSA.
Finally, Interpower Corporation maintains lot code traceability on all components used in manufacturing power cable assemblies. This allows our customers to meet the high demands for quality and traceability placed on them by their customers.
Interpower Corporation offers a wide variety of special services to benefit you and your customer. Special labeling is available for any power cord or cord set, with a wrap label, flag label, or hot stamp. We can also provide special packaging for all of your parts, in the way of individual bagging, hanking, coiling, or boxing. For further convenience, individually boxed and bagged parts can be labeled on the package. We can also add the CE Marking to assemblies targeted for European markets.
Warning: This product contains chemicals, including lead, known to the State of California to cause cancer, birth defects, or other reproductive harm. Wash hands after handling.