A NEMA power cord is a power cable whose power plug is used for AC mains electricity in North America and other countries that use the standards set by the US National Electrical Manufacturers Association (NEMA). There are many NEMA power cord types with different NEMA connectors. The NEMA connectors represent either the power plugs or the receptacles/outlets that allow the NEMA power plugs to be inserted into.
The following figure lists the common forms of the NEMA connectors ranging from 15A to 60A in different power cords.
Figure 1: Overview of NEMA Connectors
Most NEMA connectors are straight-blade and non-locking connectors labeled with two numbers and a letter “P” or “R” followed by the second number. The two numbers are separated by a dash. The meanings of NEMA code is shown on the table below:
|P||plug||NEMA 5-15P: it's a 125V 15A plug; NEMA 5-15R: it's a 125V 15A receptacle|
|Number before the dash||the NEMA type related with voltage rating|
|Number after the dash||the current rating|
Note: There are a few special codes such as L21-30P, L15-20P, L22-20P, etc. Numbers prefixed by “L” are curved-blade, twist-locking connectors. This article does not introduce these NEMA connectors in detail.
Different NEMA connectors form different NEMA power cord types. There are two main classifications of NEMA connectors, namely straight-blade and locking. Straight blades are mostly found in regular consumer electronics and the metal conductive blades are often informally called "prongs" (3-prong power cord, for example). NEMA straight-blade or non-locking connectors use blades of various flat and folded shapes except for the round pins used on grounding connectors. One can detach the NEMA power plugs from the outlets or receptacles by pulling back on the plug body. The locking connectors are reserved for more industrial uses and will have curved blades that allow the plug to be twisted and locked into the receptacle.
NEMA connectors can be divided into different subtypes according to different classifications as well. The straight-blade or non-locking NEMA connectors include 25 subtypes such as NEMA 1, NEMA 2, NEMA 3, NEMA 24, NEMA TT-30, etc. The locking NEMA connectors include 24 subtypes such as ML, NEMA L1, NEMA L2, NEMA L23, etc. What’s more, different NEMA connectors have different specification codes as their identifications such as 1-15P, 1-20P, 5-15P, 5-20P, etc. The following part will introduce the most commonly used NEMA connectors (all are straight-blade ones) with different designations.
NEMA 1: NEMA 1 connectors support 2-wire non-grounding devices rated for 125 V. Although the NEMA 1 plugs in 2-prong power cords are ungrounded, they are still popularly used by manufacturers of small appliances and electronic devices because of the low cost and compact size. For example, they are commonly seen on basic lamps or non-grounded hair dryers. In addition, they are upward compatible with modern grounded NEMA 5 receptacles. The common NAMA 1 codes include 1-15P, 1-20P, 1-30P, etc.
Figure 2: NEMA 1 Connectors
NEMA 5: NEMA 5 connectors support three-wire (hot-neutral-ground) grounding devices rated for a maximum volts of 125 V. Sometimes, a NEMA 5 plug in a NEMA power cord is called an Edison plug. The NEMA 5 plugs are basic plugs found on most power connections between PDUs and IT equipment, including network switches, routers, computers, surge protectors, etc. The 5-15P is the most common NEMA 5 connector used in the US. And the NEMA 5-15P is a grounded version of the 1-15P. For safety concerns, please note that do not remove the ground pin (the third prong) to make a three-prong plug fit a two-prong outlet.
Figure 3: NEMA Power Cord With NEMA 5 Connector
NEMA 14: The NEMA 14 connectors are four-wire (hot-hot-neutral-ground) grounding connectors available in ratings from 15 to 60 A. The voltage rating is 125/250 V. Normally, NEMA 14-30 and 14-50 devices are the common non-locking devices used in electric clothes dryers and electric stoves respectively. What’s more, NEMA 14-50 devices are often found in RV (recreational vehicle) parks for powering large RVs.
Figure 4: NEMA 14 Connectors
NEMA TT-30: The NEMA TT-30 (TT stands for Travel Trailer) connector is a 120 V 30 A recreational vehicle standard, also known as RV 30. The orientation of a NEMA TT-30 connector is the same as the NEMA 5’s. Therefore, adapters are available with the TT-30P plug on one side and a 5-15R or 5-20R receptacle on the other side. The NEMA TT-30R receptacle is commonly available in nearly all RV parks.
Figure 5: NEMA TT-30 Connector
Figure 6: Male NEMA TT-30 to Female NEMA 5-15R Adapter Plug
Actually, NEMA and IEC are the two most common standards for power cords used in North America. They are normally used together in many situations. For example, NEMA 5-15P, the most commonly used NEMA power cord, uses NEMA connector or plug on one side and IEC connector on the other side. Like NEMA power cord types, there are many types of IEC power cords as well. For more details, refer to Different Power Cord Types.