Plugging in Navigating international power-connection standards

Look at an electrical outlet outside the U. S. and you’ll probably see an unfamiliar plug pattern. There are 18 different plug patterns used around the world. In addition, countries around the world use different ac mains voltages and frequencies. North America, part of South America, and a few other countries that run on 60 Hz. Most of the rest of the world runs on 50 Hz. However, some countries, such as Japan, run on both. While the voltages in most industrialized countries are typically 120 or 230 Vac, voltages can run anywhere from 100 to 250 Vac. Again, some countries use multiple voltages.

When configuring electrically powered equipment for use outside the U. S., cutting off the “wrong” plug and rewiring the “right” plug or using an adapter does not solve the problem. Once you change the cord, as when rewiring the “right” plug onto it, the cord loses its regulatory approval — which could also affect the approvals on your equipment. Use of country-specific adapters is fine for traveling, but they are not recommended for use on a piece of industrial equipment; the adapters are not approved, so your cord and equipment may lose approvals.

All developed countries and many of the developing countries have electrical safety standards. As a result, most have electrical testing agencies. The U. S. has several, including Underwriters Laboratories and CSA International; Germany has VDE; Sweden has Semko, and so on. Most developed countries require some sort of a third-party test and approval before equipment can be sold internally. Many European countries will accept VDE approval on parts used there. In most European cases, the national standard will simply be a translation into the local language of the applicable International Electrotechnical Commission (IEC) or Cenelec document. Any deviations are noted in the front of the publication. UL and CSA have adapted some IEC standards but, for the most part, their standards are independent of IEC and Cenelec.

Plugs and sockets can be categorized by their class and polarization. Class I plugs and sockets have the ability to provide grounding. The grounded plug and socket must have at least three pins or contact points. Class II plugs and sockets have only two electrical contact points, line and neutral, and use two-wire cables.

A polarized plug-and-socket configuration has two meanings. The first is electrical polarization. In this situation, there is an assigned method of wiring the plug or receptacle. The wiring is done so the connection between the line wires and the neutral wires on the plug and receptacle always make contact. This polarization pattern provides a method of controlling the entry of electricity into the equipment.

The second form of polarization is pin polarization. Pin polarization means there is only one way to insert a plug into the socket. This is based on the alignment of the pins in the plug to the holes in the receptacle or socket. Some plug patterns, such as the Schuko, are neither plug nor pin polarized.

North American plugs
The North American plugs, connectors, and receptacles are described in standards published by the National Electrical Manufacturer’s Association (NEMA) in the U. S. and Canadian Standards Association (CSA) in Canada. The standards identify unique pin and receptacle configurations based on amperage and voltage ratings. Both straight blade and locking configurations are included in the standards.

An accompanying chart shows the different pin configurations. Notice that the blade position changes or is a different shape to prevent accidentally plugging a 30-A plug into a 15-A receptacle. The NEMA 5-15 straight-blade configuration is used most often in the U. S. and Canada.

The NEMA pattern and numbering system is made up of four main identifiers. The first can be a blank space or have the letter L. This determines whether the connection is a straight or locking blade device. For example a 5-15 plug means the blades are straight, but a L5-15 plug denotes a locking version.

The second identifier is a number. The first digit listed determines the voltage rating. The 5 in a 5-15 corresponds to the voltage rating of 125 Vac, while the 6 in 6-15 identifies a rating of 250 Vac. The rating given is the highest voltage allowed for a device by the standard.

The third identifier is also a number and it identifies the amperage rating for the device. A 5-20 has a rating of 20 A. The amperage rating, like the voltage rating, is the highest amperage the standard allows for use with the device.