Server is like a large computer group which is used to manage network resources. It requires power supply to support working. Server power cords are the basic assemblies to achieve the connection between servers and PDU (Power Distribution Unit). However, the designs of them vary from country to country in terms of voltage and connector types. Thus, to determine what type of power cord your server or system requires, you need to know the country or region in which your server or system will reside, your server or system model, and the voltage and amperage of your power supply. In order to regulating the use of the power cords and allowing easy selection for users, there are some standards which are used to define the connectors. In this post, we will have a brief introduction to server power cords.
We can regard a power cord as three parts—cord, plug and receptacle. Among them, the plug and receptacle are also called connectors collectively (will be explained in details in the next part). The three parts of a server power cord are shown as following:
- Cord—Main section of insulated wires of varying length and of a thickness determined by its current rating.
- Plug—Male connector for insertion into the AC outlet providing power. The physical design and layout of the plug’s contacts meet a specific standard.
- Receptacle—Female connector that generally attaches to the equipment. The physical design and layout of the receptacle’s contacts meet a specific standard.
There are many different types of power cord connectors used all over the world. Standards for these connectors are often set by individual countries. In the US, the most common type of power cords have an IEC (International Electrotechnical Commission) connector that plugs into the server and a NEMA (National Electrical Manufacturers Association) connector that plugs into the power source. The IEC has published international standards for alternating current interconnections between equipment. NEMA is a US based organization that establishes a wide range of standards for US electrical devices.
IEC 60320 is a set of standards from the IEC specifying non-locking appliance and interconnection couplers for connecting power supply cords to electrical appliances up to 250 V. When equipment uses connectors that comply with this standard, worldwide compatibility is achieved. The IEC 60320 C13 / 14 connector type is seen on almost all personal computers and monitors. It has a rating of 10 A and the female connector end is defined as C13 while the male connector end is defined as C14. The IEC 60320 C19 / 20 connectors are rated for 16 A and have a female connector end called C19 and a male connector end called C20. C19 / 20 connectors are commonly used for devices such as some servers and UPS (Uninterruptible Power Supply) systems. The most commonly used type for Dell, HP and IBM servers is the the C13 and C14 connectors.
NEMA connectors are power plugs and receptacles used for alternating current mains electricity in North America and other countries that use the standards set by the NEMA. According to different configuration, such as the number of poles, number of wires, voltage, and whether single- or three-phase, there is different numeral preceding the hyphen in NEMA nomenclature. And with different rating of the device in amperes, the numeral following the hyphen is also different. In addition, plugs and receptacles are designated with “P” and “R” in the nomenclature. If there is an “L” in the nomenclature, it means that the plugs and receptacles are twist locks. For example, NEMA 5-15P is the common 125 V two-pole, three-wire plug rated 15 A. NEMA 5-15 plugs and receptacles are the most common server power cord connector types used in the US.
When getting power cords for servers, there are various jacket types and AWG (American Wire Gauge) choices to make. How to know which one you actually need for your server power cords?
There are many kinds of jacket types which are used in power cord design. In order to better distinguish the different jacket types and features, a series of code letters is used to describe the jacket, as the following shown. Each letter has its own meaning describing the material used in the jacket, the voltage rating, the jacket’s resistance to the elements, or other factors which is defined in the UL 62 standard and stamped on the jacket.
- S—Service Grade. This means the cord is 600V rated.
- SJ—Junior Service. Meaning 300-Volt rated.
- T—Thermoplastic. The wire is coated in PVC.
- P—Parallel. These are the types of cords where each conductor insulated separately as in a typical lamp cord.
- O—Oil-Resistant. One “O” means the jacket is resistant to oil. Two “O”s means the jacket as well as the insulation inside the cord are oil resistant.
- W—Weather-Resistant. Essentially, these cords are outdoor-rated. They include resistance to wet conditions as well as UV protection.
- V—Vacuum Type. Flexible jacket originally used for vacuum cleaners, but is now found on a wide variety of products.
In addition, different jacket type corresponds to different parameters, such as permitted wire gauge, permitted of conductors etc. The table below shows the features of some common jacket types. Among them, SJT and SVT are the more common jacket types used in server power cords.
|Jacket||Permitted Wire Gauge||Number of Conductors|
|SPT-1||20-18||2 or 3|
|SPT-2||18-14||2 or 3|
|SPT-3||18-10||2 or 3|
|NISPT-1||18-16||2 or 3|
|NISPT-2||18-16||2 or 3|
|SVT||18-16||2 or 3|
|SJT||18-10||2 to 6|
|ST||18-2||2 or more|
Note: The -1, -2, and -3 behind the letters indicates the thickness of the jacket. -1 is thin, -2 is medium and -3 is thick.
There is a close relationship between cable length, amperage and wire gauges. See the table below, the different amperage corresponds to different AWG. The higher the amperage rate, the larger the number of AWG is. In addition, if the length of the cord is increased, the wire gauge will have to be increased. Wire gauges are also related with the jacket type since different jackets can accommodate different wire gauges and number of conductors inside the power cord.
|Amperage||Recommended Wire Gauge|
|7 A||20 AWG|
|10 A||18 AWG|
|13 A||16 AWG|
|15 A||14 AWG|
|20 A||12 AWG|
Power cords used for server and PDU seem like the bridges between power supply and devices. Thus, to choose a suitable power cord for your server requirement is very important. The standards of plugs and receptacles specify the use of the power cords and make selection become easy. Jacket types and wire gauge are chosen depending on the server or system model, and the voltage and amperage etc. In addition, different jacket colors are used for unique maintenance. Fiberstore offers the most extensive line of IEC and NEMA server power cords. The most common IEC C13/C14 for Dell, HP, IBM servers and NEMA 5-15P in the US are available. They come in splitter cords (supports 2 or more receptacles), angled cords and locking featured cords. The color, length, angle of cable can be customized. For more details, please contact us via firstname.lastname@example.org.
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