What are Electrical Plugs?
An electrical plug or power plug is a device for transmitting and receiving electrical current between a receptacle and the circuitry of an appliance.
Normally, these plugs have prongs or pins that fit into an outlet and house a supportive casing made out of plastic. The prongs plug into the openings of a socket or receptacle and join the main power source to the appliance.
Standard electrical plugs come in different types used around the world in homes, industries, and commercial settings. Depending on the country of use, they differ in the number and size of pins, voltage, current ratings, and other requirements.
Types of Electrical Plugs
All the Electrical plugs typically feature either two or three prongs
Two-Pronged Plugs.
A two-pronged plug has one prong that is “hot,” denoted by a colored line, and the other termed “neutral” has no marking. When a two-prong plug is inserted, it has one prong that is “hot” and the other that is “neutral.”
The hot prong contacts the hot slot of the receptacle. The current flows into the receptacle as the load is powered.
The neutral prong goes into the neutral slot and the current flows out and completes the circuit. Two-pronged plugs are very easy to put into any two-slot receptacle.
Three-Pronged Plugs
Three-pronged plugs come with an extra grounding or an earthing pin, which is attached to the ground wire of the electrical system. This pin is placed lower than the hot and neutral pins and normally does not let current pass through it.
The earthing pin allows stray electricity to be redirected away from the appliance due to a fault, short circuit or surge thus avoiding damage to the appliance or electrocution.
It helps alleviate electrocution, electrical fires, damage to the appliance by redirecting excess current to the ground. Nowadays, three-slot receptacles have become commonplace to install in new construction for enhanced safety.
High power appliances such as flat irons, HVAC systems, industrial machinery, sensitive electronics and even toasters use three-pronged plugs.
Furthermore, devices that come with metal casings like computers and game consoles use them since stray electricity can cause shocks. Use of the grounding pin prevents users from stray currents.
NEMA Plugs (Type A, B)
NEMA plugs follow the criteria set by the National Electrical Manufacturers Association (NEMA), which is an association of manufacturers of electrical and medical imaging equipment.
NEMA standards are often used in the United States and Canada, but are used in other areas too. NEMA has several designations for plugs, one of which is Type A and Type B.
Type A (NEMA 1-15) Plugs
Type A NEMA plugs do not have ground and they possess two rectangular parallel rods (prongs). They have a current rating of 15A and a voltage rating of 125V. The prong length ranges from 15.9 to 18.3 mm, with a spacing of 12.7 mm between the prongs.
Type A plugs can be found with and without polarization. In the case of Polarized plugs, the neutral pin is broader than the hot pin which ensures that it can only be inserted in a certain way.
These are widely used in North America and Mexico where the neutral and hot pins are 7.9 mm and 6.3 mm wide respectively. Non-polarized plugs with identical width prongs, non-polarized plugs are more common in Japan.
While non-polarized plugs fit in polarized sockets, the opposite is false. Type A plugs can be used interchangeably with Type A and Type B sockets; Type A plugs have holes cut at the end of their prongs.
With type A plugs, secured connection is ensured by filling holes while the prongs sit in the receptacle. Bumps on the outlet’s contact wiper fill these holes, preventing the plug from being dislodged.
Specialized sockets can use rods to lock inserts into these holes. Other uses for these holes include factory sealing.
Other sockets use spring-action blades in place of a contact wiper, which grip the sides of the prongs, offering another way to secure the plug without needing holes in the prongs.
Type B (NEMA 5-15) Plug
Type B electrical plugs or the North American 3-pin plug has two flat, parallel prongs with a round grounding pin sticking out as the third prong which is a power source. They are grounded.
The ground pin is longer than the hot and neutral pins to ensure that connecting the ground takes place prior to the voltage connection. The hot and neutral prongs are 1.5 mm thick, 15.9-18.3 mm long, and 6.3 mm wide.
And also ground pin, which has a diameter 4.8 mm with a length of 3.22 mm longer than the flat prongs.
Type B plugs are used in B and 15A and 125V and is in common use in America North, Mexico, China, Japan and other users of type A plugs. In Japan, the design of the Type B plugs varies slightly compared to those used in the United States.
CEE 7 Standard AC plugs (Type C, E, F)
CEE 7 Standard AC plugs belong to the publication “Specification for plugs and socket-outlets for domestic and similar uses”. This standard is maintained by the IECEE regulating the domestic electrical connectors utilized in Europe.
There are countries like the United Kingdom, Ireland, Malta, Switzerland, Italy and Cyprus that do not use CEE 7 plugs and sockets are not primary CEE 7 power connectors.
Type C (CEE 7/16 and CEE 7/17) Plugs
Around the world, type C is the most common electrical plug in use. It is a plug with two round pins that is not grounded and unpolarized. There are two variations of Type C plugs:
Europlug (CEE 7/16).
Europlugs have two pins measuring 19 mm long and 4 mm in diameter. The pins are set 18.6 mm apart at the base and 17.5 mm at the tip. The lower portion of the pins is insulated, with 10 mm of their length from the base covered.
The pins are flexible to a degree, which enables them to be inserted into sockets designed for rounded pins with diameters ranging from 4.0 to 4.8 mm and 17.5-19 mm apart.
Europlugs are rated with 2.5A; due to the low current capability Europlug offers, Europlugs can only be used for low energy applications.
Europlugs are the most widely used exercise of Type C plugs.
Contour Plug (CEE 7/17).
Contour plugs have two pins measuring 19 mm long and 4.8 mm in diameter. The pins are spaced 10 mm apart, giving them a narrower spacing than Europlugs.
Unlike Europlugs, contour plugs do not have an insulated sleeve. The sitting cover in electrical plugs increases the safety of their use.
Contour plugs come with a maximum rating of 10A or 16A which means they can be used with heavier energy appliances.
Type E (CEE 7/5) Electrical Plugs
Type E electrical plugs have two round pins that are 19 mm long, spaced 190 mm apart, and 4.8 mm wide.
They have a female contact or hole that receives the socket’s earthing pin which is 14 mm long and 4.8 mm wide. Male pins of Type E plugs are arranged ex-centrically, preventing rotation of the plug in the socket.
Type E sockets are also known as French sockets since they are widely used in France, Belgium, Slovakia, and Tunisia. They are rated at 16A and are compatible with TYPE E and TYPE F sockets.
Type F (CEE 7/4) Plugs
The Type F electrical plug has the same pin size as the Type E plug. However, its pins are not completely round. Type F plugs have two earthing clips located on the upper and lower part of the plug housing rather than a female earthing contact.
These clips are 16 mm from the midpoint between the pins which hold the plug in position. Also, these plugs have plastic ridges on both the left and right sides to secure the plug better when used as a wall-mounted socket.
Type F plugs are rated for 16A, and they cannot fit into Type E sockets. They are widely used in Germany, Austria, the Netherlands, and Spain, and are referred to as Schuko plugs.
CEE 7/7 Plugs
The CEE 7/7 plug is a combination of Type E and Type F plugs, so it works with both types of sockets.
For Type E sockets, it has a female earthing contact while for Type F sockets it has two earthing clips on the plug housing. CEE 7/7 plugs are used in regions that have both Type E and Type F standards.
British Standard Plugs (Type D, M, G)
BS 1363 is a British standard outlining the safety, construction, electrical and mechanical testing, dimensional accuracy, and marking requirements for plug and socket systems in the UK.
This standard has also been adopted by other countries, including India, Malta, and South Africa.
Type D (BS 546) Plugs
With a power rating of 5A, D-type electrical plugs—which are frequently used in India, Sri Lanka, Namibia, and Nepal—are equipped with three round pins that form a triangle.
Each of the two ‘live’ pins (hot and neutral) has a length of 14.9 mm and a diameter of 5.08 mm, and they are spaced 19.1 mm apart.
The central earthing pin, however, measures 20.6 mm in length and 7.06 mm in diameter. Furthermore, the odd-shaped pin set in Type D plugs ensures that polarity reverse is not possible.
Plugs Type M (BS 546)
Plugs Type M have the same set of pins as plugs Type D. However, Type M has larger powering pins capable of accepting 15A of current as well as larger hot and neutral pins.
The central earthing pin is 28.89 mm in length and has a diameter of 8.71 mm while the hot and neutral pins are 18.94 mm in length, 7.06 mm diameter, and 25.4 mm apart.
Due to the higher current capacity, Type M may be used along with Type D plugs on appliances that utilize higher power.
Type M is mostly in use at South Africa, Swaziland, Lesotho, UK, Israel and the UAE. The South African version has an insulated sleeve on both pins and bare connectors.
Type G (BS 1363) Electrical Plugs
The Type G electrical plugs have three rectangular pins arranged in a triangular layout, as well as a fuse. The central earthing pin is 4mm by 8mm by 22.7mm. The hot and neutral pins are 4mm by 6.35mm by 17.7mm long, with a center-to-center distance of 22.2mm.
The sleeves of these pins are insulated, but the earthing pin is not. British sockets have shutters that block access to the hot and neutral pins for foreign objects.
Type G plugs also have a fuse of 3A or 13A, the higher rating is used for more demanding appliances. This is what makes the Type G plug and socket system one of the safest for users and equipment.
Type G plugs are designed specifically to be used with Type G sockets, and cannot be used with other types of plugs.
Type G plugs, also called `Commonwealth Plugs´, are widespread in use in the UK, Ireland, Hong Kong, Singapore, Cyprus, and Malta.
Type H (SI-32) Plug
Type H electrical plugs incorporate 3 round pins set at an equal distance of 19mm from each other, with two of the pins, the neutral and the hot, measuring 4.5mm in diameter and 19mm in length, while the earthing pin is 9.5mm from the center of the two other pins. Moreover, type H plugs are grounded and can be used for a maximum power of 16A.
Type H plugs can only be fit into type H sockets. This means that although type H sockets can take type C plugs, they are not suitable for type E or F plugs.
There are also concerns with type H plugs as they do not come with a covering sheath which makes them dangerous when partially inserted.
In addition, type H plugs do not work outside of Israel and Palestine.
AS 3112 Type I Socket
Type I plugs feature two flat, 30 degree, hot & neutral pins along with an eathring pin. Both the hot and neutral pins are 17.3 mm long and 6.3 mm wide.
They are also spaced at 13.7 mm. The pins are insulated while the earthing pin is 20 mm long which is positioned vertically. The hot and neutral pins are positioned 10.3 mm from the center of the plug with a distance of 6mm for 10 A plugs.
However, the current rating goes because plugs with 15 A will be lowered to 8 mm. There are 20 A Type I plugs with different sized prongs. Ungrounded versions of Type I plugs are also available.
The/sockets/plugs with a lower current rating can fit into sockets with higher ratings but the higher rated plugs and sockets cannot fit.
Type I plugs are commonly used in Argentina, Australia, New Zealand, Papua New Guinea, China, and other pacific islands.
The Type I Chinese plugs have the earthing pin above the other two with a mark of 1 mm longer than the standard. They plug from Australia is interchangable with the Type I socket in China.
Type I plugs are detailed in AS/NZS 3112 – the Australian and New Zealand Standard for Plugs and Sockets. Description in English.
Type J (SN 441011) Electrical Plugs
Type J electrical plugs have 3 round pins, which are about the same size as those of Type C plugs. The hot and neutral pins are 19 mm apart, and the earthing pin is 5 mm offset from the vertical line between hot and neutral pins.
All pins are 19 mm long and 4 mm in diameter and are fully insulated. The construction of Type J plugs ensures that they cannot be reversed. These plugs are 10A rated.
Type J plugs are similar to Brazilian Type N plugs but cannot fit into Type N sockets due to the different locations of the earthing pins.
They are used in Switzerland and Liechtenstein. They are classified as Type 13 Plugs in SEV 1011 – the Swiss Standard of plugs and sockets for the home.
Type K (DS 60884-2-D1) Plugs
The electrical Type K plugs consist of two round pins and a U-shaped earthing pin. Each hot and neutral pin measures 4.8 mm in diameter, 19 mm in length, and the distance between them is 19 mm.
The U-shaped earthing pin measures 6.5 mm in diameter, 14 mm in length, and 4 mm in thickness. Like the Type E plugs, they are also similar with a few distinctions. K Type plugs differ from E type plugs with the design and gender of the earthing contact.
K Type plugs are designed in such a way that they cannot allow polarity reversal. Their maximum current rating is 16 A.
In Denmark and Greenland, Type K plugs are in use. They are included in DS 60884-2 D1 which is the standard based on Denmark regarding the construction of plugs and sockets for households and similar application.
Type L (CEI 23-16-VII) Electrical Plug
Type L electrical plugs come with three round pins arranged in straight line with the earthing pin located between the hot and neutral pins. There are two versions of Type L plugs, differing from each other in current rating and dimensions of the pins:
- The 10A variant has a pin diameter of 4mm, a length of 19mm and a distance of 19mm between the hot and neutral pins. The distance of the center of the earthing pin to the center of hot or neutral pin is 9.5 mm.
- The 16A variant has a pin diameter of 5mm, a length of 19 mm and a distance of 26mm between the hot and neutral pins. The distance of the center of the earthing pin to the center of the hot or neutral pin is 13 mm.
Due to dimension differences, the 10A and 16A Type L plugs are not interchangeable. The unpolarized nature of Type L plugs, allows them to be inserted into the socket in any direction, without concern for alignments.
Countries such as Italy, Chile, Uruguay and select North African nations use type L plugs.
Type N (IEC 60906-1) Electrical Plugs
The functionalities of ‘N’ Type electrical plugs comprises of three round pins arranged in a triangular configuration. Like other types, this one also has three variants: 10A, 16A, and 20A. Each of the variants also comes equipped with pins that are 19 mm long.
Their diameters differ, though, with 4mm for the 10A version, 4.5mm for the 16A version, and 4.8mm for the 20A version. Furthermore, the pins have an insulated sleeve 10 mm in length that covers part of the pin.
Between the hot and neutral pins, the distance center-to-center is 19 mm. The average distance of the earthing pin from the midpoint of the line joining the hot and neutral pins is 3mm.
Therefore, the distance from the Type N plugs with Type J plugs cannot be used because this distance is less than the former’s (5mm).
In Brazil, the Type N 10A and 20A plugs are used whereas in South Africa the plugs are using the 16A version.
Type O (TIS 166-2549) Electrical Plugs
Each of the three round pins on Type O electrical plugs has a diameter of 4.8 mm. The neutral and hot pins are 19mm long and have an insulated sleeve of 10mm along their length. The earthing pin is 21.4mm long.
The distance between the hot and neutral pins is 19mm, but the earthing pin is 11.89mm off center from the horizontal neutral and hot pin. Type O plugs have an operational value of 16A.
Type O plugs are not used outside Thailand and are described with the standard TIS 166-2549. This plug and socket system was released in 2006 and is still being implemented.