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Interpower Corporation P.O. Box 115 100 Interpower Avenue Oskaloosa, IA 52577 (USA)
Copyright 2009.
All Rights Reserved
Interpower Corporation P.O. Box 115 100 Interpower Avenue Oskaloosa, IA 52577 (USA)
Copyright 2009.
All Rights Reserved
Interpower Connections, August 2009 edition, looks specifically at how to choose the correct North American power connection devices for any application. To also assist you with North American power connection devices, Interpower Corporation is offering, for free, our Interpower NEMA wall chart. You can download the wall chart as a PDF, print it off and post it or save a copy for future reference. Upcoming editions will take a look at other subjects that we hope will be of interest to both experienced and new designers alike. Should you have a question that Connections has yet to answer, please email us at info@interpower.com.
International equipment manufacturers face many challenges when designing equipment for use in the North American market. One area that is often overlooked or overshadowed by other issues is the choice of connection devices for use in connecting to the mains supply or distributing power throughout a system. It is easy to assume that, like other countries, there are one or two common plug and socket patterns and mains systems to choose from in the North American countries. However, this is not the case. Not only are there numerous mains voltage systems and connections systems available, but there are other issues to consider as well. In this edition of Connections, we will focus on the primary power connection system used in North America: the NEMA family of power connection devices. We will also discuss some of the issues that need to be considered when designing equipment and specifying these type of devices.
North America has the unique distinction of having multiple mains power systems available for use by the consumer and each system has the potential to use more than one plug type, based on numerous standards. So how do you identify the correct plug or receptacle needed for an application? How do you keep them all straight? Luckily, there is one primary system used throughout North American that can provide some focus and help designers choose the correct system. There are also some other considerations we will discuss, that will help you to further narrow your choices.
The primary electrical connection system used throughout North America is the NEMA (National Electrical Manufacturer’s Association) system as outlined in the NEMA WD6 publication. This requirement was originally developed with the intent of helping users identify correct patterns for various applications, while simultaneously providing a system for minimizing the possibility of unsafe interchangeability between unlike configurations. The NEMA system categorizes its patterns by both amperage rating and the voltage rating of the system with which they are to be used, and allows for both straight blade and locking versions. For instance, the common everyday household receptacle is known as a NEMA 5-15. The “5” in this designation means that this item is intended for use in a 125V, 3 wire system. The number “15” indicates that the system is capable of supplying a maximum of 15 amperes of current. This NEMA 5-15 is a straight blade device. Using this basic understanding of the NEMA system and making several key observations about your application needs will be of great significance in identifying the products you need. So, what are the basic issues you should consider when specifying which NEMA pattern to use?
Locking or Straight blade?: Straight blade NEMA plug configurations use flat sided blades that simply slide in and out of the mating receptacle. These are fine for standard use where the connection is stationary and not subject to movement or vibrations that could cause the plug to come loose from the receptacle. Where movement and vibration are an issue, the locking plugs might be better suited. These NEMA plugs utilize rounded and odd shaped pins that require the plug to be inserted into the receptacle and twisted a slight bit at the end of the insertion, in order to ensure connection. This twist also locks the plug and receptacle together, preventing accidental disconnects. Locking NEMA configurations are differentiated by an “L” in the designator (ex. NEMA L5-15P)
Single Phase or 3-phase voltage: This is an important consideration. There are basically 12 different single and 3 phase voltage groupings used in the NEMA system. Single phase systems typically have one line and one neutral or two line wires and may have a ground connection. Three phase systems use 3 line wires, where each hot leg is 120° out of phase with the others. Single phase system will typically use 2 or 3 wires and 3 phase systems will use 3, 4, or 5 wires, with 4 or 5 being more common.
Current Rating: Knowing the amperage that your equipment will need, can also drastically narrow down the NEMA pattern you would need to use. There are 5 different amperage levels in the straight blade versions: 15A, 20A, 30A, 50A, and 60A. There are 3 amperage levels in the locking devices: 15A, 20A and 30A.
Class I and Class II: This consideration is most important when dealing with single phase systems, but could apply to 3-phase as well. A Class I system means a ground connection is used. In Class II systems, the ground is absent. These systems typically have additional safety regulations that must be met. There are only a few Class II options available in the NEMA system, therefore, if this is readily known, it can quickly aid you in narrowing down the possibilities.
When specifying NEMA devices for an application, there are some additional issues that may need to be considered, based on the style of the device needed or where specialized requirements may exist. While these factors may not always be applicable for every application or for every manufacturer, there are times when they are critical to the selection of the correct NEMA devices to ensure compliance with safety agency or standard requirements.
Choose the correct style: NEMA devices come in multiple body styles, based on intended use. Cable mount plugs and connectors are typically specified for power cord and cordset applications. These applications range from connecting to the mains outlet, to power distribution inside a large system or to peripherals. Wall receptacles are used to provide points of power access at the wall or in distribution strips or centers, most commonly. Inlets and outlets are typically mounted to the equipment chassis and aid in the connection of the devices to the mains (through a detachable cordset) or for connection of one piece of a system to another, such as a primary piece of equipment to a peripheral. Using the wrong style for an application could cause safety issues and affect approvals.
Hospital Grade Devices: NEMA devices used in hospital settings where patients could be connected to equipment, are required to meet special requirements as required by medical equipment standards UL 60601-1 and CAN/CSA C22.2 No. 60601; power supply cord standards UL 817 and CAN/CSA C22.2 No.21; and attachment plug standards UL 498 and CAN/CSA C22.2 No. 42. The requirements basically center around the need for a more robust plug and a more reliable ground connection. Hospital grade devices carry a mandatory “green dot” marking, which signifies these devices as tested and approved to the requirements in the standards listed above. Manufacturers and designers specifying medical grade devices need to be aware that UL 498 and CAN/CSA C22.2 No. 42, only allow the straight blade patterns of the NEMA 5-15, NEMA 5-20, NEMA 6-15, and NEMA 6-20 to be Hospital Grade approved. This means no other NEMA devices currently are allowed to carry the Hospital Grade “Green Dot” approval, including the common NEMA 1-15 (Class II) family and locking devices. It is therefore imperative not to design equipment with the expectation that you will find a Hospital Grade device in one of the other NEMA families.
Isolated Ground Circuits: These special circuits are used to isolate the ground circuits from harmonic distortion, protecting sensitive equipment from operational degradation, disruption, and possible damage. These circuits require special NEMA devices be used to identify them, to prevent unintended items (vacuums, drills, etc.) from being plugged into the system and inadvertently introducing unwanted distortion. These devices are typically orange and are marked with a triangle on the face. These circuits can also be found in hospitals, as well as, large computer rooms, data centers, test labs, and the other similar applications.
Special Environmental Factors: In some instances, special resistance measures to an environmental influence may be necessary or desired. There are a number of these specialized cases that one should be aware of if the need should ever exist.
Corrosion resistant devices may be needed where water and chemicals may be present that could cause corrosion to occur quickly. Such applications might be marine products, food processing or producing applications or motor vehicle maintenance facilities.
Theater applications often require all black parts so that these do not stand out on or around stage and distract from the show.
Dust resistant inlets and outlets are available on the market as well. These panel mounting devices utilize an attached flexible cover lid and a similar boot on the back. The cover lid and boots are intended to keep particulates, such as dust, from entering into wire connection areas at all times, and around the pins and contacts at the face, when the devices are not in use. This protects these sensitive regions from potential damage that can be caused by the dust. Damage can range from abrasion to corrosion, depending on conditions and the type of particulate. Applications might include construction sites, and other portable indoor/outdoor uses where concrete, gravel, or other common dust particulates might be present in high concentrations.
Despite the fact that the NEMA WD6 standard can appear intimidating due to the number of possible configurations, using the information presented here should quickly help you identify the correct device for your application. back to top
Interpower's Angled NEMA 5-15 power cords are for equipment rated up to 15 amps with
service at 125VAC. They are CSA and UL approved. The Interpower angled NEMA
5-15 power cords are available with 18/3, 16/3, and 14/3 AWG cable in stock
lengths of 6, 8, and 10 feet. Applications would include equipment designed
for business, medical, or testing.
Interpower angled NEMA 5-15 power cords are configured with one of eight different angles (45 degree increment) of the NEMA 5-15 plug and terminated with bare conductor wires. This allows designers to reduce the clearance space required behind or under equipment by specifying the angled plug that is appropriate for a particular application.
Custom lengths, special packaging, and color (black, red, white, yellow, orange, or tan) options are available with a 1 week manufacturing lead-time and no minimum order requirements! Same day air shipments are available for stock item orders received by 6:00 p.m. Central Time. For ordering and technical information about the new Interpower angled NEMA 5-15 molded power cords, please contact our Customer Service Department at 800/662-2290 or visit us at www.interpower.com. back to top
Here is your chance to request your free copy of our Interpower NEMA wall chart. The Interpower NEMA wall chart will make it easy for you to specify the North American power connection device you need, when you need it. With this handy wall chart, you will be able to find the Interpower part number you need, easily and quickly. Click on the chart to download your copy or request a hard copy by emailing connections@interpower.com with the subject line: NEMA.