What are NEMA Connectors?
National Electrical Manufacturers Association (NEMA) is an association that sets standards to ensure the safety and national adaptability of electrical products. The receptacles or plugs that follow these standards are called NEMA connectors. These connectors are used mainly in North America, where these wiring instruments have current ratings ranging from 15 to 60 amperes and voltage ratings ranging from 125 to 600 Volts.
NEMA connectors vary in sizes, shapes, and combinations of contact blade widths depending on the voltage or electric current they are rated to carry. The reason for these variations is to create unique non-interchangeable combinations of these plugs. In the United States, electrical receptacles and plugs follow the quality standards of NEMA.
The most common connectors seen on domestic setups or houses and residential areas are the NEMA 1-15P (no ground, two poles) and NEMA 5-15P (grounded, two-pole). These have bodies made up of rubber and prongs made up of steel or brass with zinc, tin, or nickel coating. For the less standard connectors or plugs with increased voltage, they may have prongs placed unconventionally.
These connectors are classified into two types: locking and non-locking.
Locking
Locking connectors have a safety system wherein it ensures connectors fit snugly together and stay connected in the plug’s accidental pull-out events. The prongs of a locking connector are curved wherein, after being inserted, it can be twisted and locked in place. These make locking connectors a reliable choice for plugs in an industrial environment where there could be chances of vibrations and some incidental impact that may disconnect a plug.
The plugs with locking connectors are engineered and specified for industrial use. These are usually identified from other NEMA connectors by having an “L” placed before the series number (e.g., NEMA L6, NEMA L7, and NEMA L10). There are smaller series for 15-ampere applications, and these are the ML series “Midget Locking.” These come in three varieties, namely: two-pole, undergrounded (125 V rating); two-pole, grounded (125 V rating); and three poles, underground (125/ 250 V rating).
Non-Locking
Non-locking connectors, on the other hand, have straight blades that can be detached from the receptacle by just merely pulling back the plug. These are commonly used for appliances, computers, and other consumer electronics.
The most common non-locking connectors used for domestic and residential are NEMA 1 and NEMA 5. These come with either two blades with a ground or two blades with no ground attached. However, the NEMA 1 connectors are slowly being phased out as the NEMA 5 connectors are required for builders.
In naming NEMA connectors, the plug configuration is seen on the first number, and it includes the number of poles, wires, and voltage. The types of grounding include two-pole three-wire, four-pole five-wire, and the list goes on. Non-grounded connectors have the same number of poles as wires because they don’t need a grounding wire. The second number in the terminology is the amp rating and is either followed by “P” for plug and “R” for a receptacle (e.g., NEMA5-15R is a 125 V, two-pole, three-wired receptacle and is rated at 15 amps).
Key takeaways
NEMA standards are established to promote safety and universality between electrical connectors in North America. These standards provide flexibility when specifying electrical requirements on installations so that the chances of selecting the wrong connectors for a specific application will be avoided.
