In the early days of the electricity craze, just after Nikola Tesla and the Westinghouse company wiped the floor with Thomas Edison’s DC power scheme, inventors around the world began working on ways to harness the fantastical energy for household work. Everybody had a different idea of how to do so. In fact, when Westinghouse standardized its operating frequency 60 Hz, it snuffed out nine other potential frequencies. The same is true for the worldwide standard of 120 and 220-240V systems—these two beat out ten other options to become the de facto voltages.
However, Germany paid little heed to the US’s choice of a 60 Hz frequency. They instead decided on a 50 Hz standard because that’s what was already being used by the BEW company, which held a monopoly on German power generation and transmission, in 1899. The 50 Hz scheme spread through Europe while the 60 Hz spread through North America. They became competing, nearly-universal standards—120V at 60Hz in North America, 220-240V at 50 Hz in Europe.
The other problem with early electrical systems: There was no easy way to tap into the power supplying small appliances. If you had a table lamp or a hair dryer or some other low voltage gadget, you’d have to knock down a wall and hard-wire it into the house’s electrical grid. Amateur inventor Harvey Hubbell is credited with creating the first appliance with a “Separable Attachment Plug.” However, instead of the cord remaining attached to the device, it would be hard wired into the system and would disconnect from the base of the gadget.
While Hubble’s preliminary plug and socket design prevented access to live wires from the home grid, many other inventors stepped up to improve his pioneering design to reduce shock and fire risks through the inclusion of grounding and electrically insulated pins, polarized shapes, and additional cut-off switches.
The most momentous of these added features arrived in 1928 at the hands of Philip F. Labre. Until then, it was uncomfortably common to receive an electrical shock when removing plugs because the pins (or prongs) would short easily short when the plug was partially pulled out of the outlet. The electrical current could travel through the person into the ground. By integrating a third pin slightly longer than the other two, Labre was able to direct all potential short circuits safely to the ground rather than through a person.
The problem with Labre’s design is that the triangular plug can be inserted into the socket in three different ways, two of which are wrong. This creates what’s known as an unpolarized plug. So engineers developed plugs that could only be fully inserted into a socket when properly oriented, thus guaranteeing a safe, polarized connection.
There are a few ways to design such a plug. […]read full post here.