Why are there Grooved Slots in the Pins of Two Pin Plugs?
Why are the Pins are Slotted in the 2 or 3-Pin Plugs?
Threaded slots are commonly found in Type A, Type B, Type C (Europlug), Type E/F, and Indian standard 2-pin and 3-pin plugs, particularly in 6A and 16A plug tops. Although these slots are not present in many other standard plug types, they appear as if they split the prongs or pins of the plug in half. These notches, located on the pins of two- or three-pin plugs, are referred to as “detent slots” or “retention grooves.”
These slots in the plugs are used as retention and detent mechanism when especially designed for wall outlets or extension cords. This feature allows spring-loaded detents or bump inside the socket to latch onto the prongs. When the prongs are inserted, the bumps fit into these holes to help secure the plug in place and prevent it from easily falling out. As a result, it improves the grip between the plug and socket contacts, preventing accidental disconnection due to slight pulls or vibrations.
- Related Post: Why Do Prongs in Electrical Plugs Have Holes in Them?
In addition, the grooves reduce stress on the socket contacts. This is because a bit of “give” prevent the pins from exerting excessive force on the socket’s internal contacts.
While not the main function, the surface features can aid in heat dissipation in high-power plugs e.g. 16A, 3-pin plugs and sockets.
Some sockets use metal contacts that push into these slots to create a more secure and stable electrical connection between the pins or prongs of plugs and blades or terminals of socket / outlet. By holding the prongs more firmly in the socket, they reduce the risk of partial insertion, which could lead to arcing or overheating.
In some plug designs, the slots make it easier to crimp or mechanically secure the prongs during assembly. The grooves make it easier for automated machines to align, grip, and assemble the pins during manufacturing.
- Related Post: Why is Earth Pin Thicker and Longer in a 3-Pin Plug?
In short, the slots in the pins of two or three pins plugs are used as a safety measure as follows:
The grooves increase the surface area and friction between the plug pins and the socket contacts. This helps to maintain a tighter connection and prevent the plug from loosening or falling out due to vibrations or slight pulling. Inserting such type of plug into a socket ensures secure electrical contact, prevention of accidental removal, reduced risk of sparking, arcing, or overheating due to a loose connection.
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Resources & Tutorials:
- Difference Between Socket, Outlet and Receptacle?
- How to Find the Voltage Ampere Rating of Plugs & Outlet & Receptacle?
- How to Wire and Install an Electrical Outlet Receptacle?
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- How to Wire a UK 3-Pin Plug? Wiring a BS1363 Plug
- How to Wire a UK 3-Pin Socket Outlet? Wiring a BS1363 Socket
- How to Wire a Twin 3-Pin Socket Outlet? Wiring 2-Gang Socket
