Power question

[silverback]

A just for interest question.
I've just purchased some new electronics. The power cable has a three pin plug at one end and a 'figure of eight' connector at the other.
Given that in the dual flex cable one side must be connected to the live terminal and the other to the neutral in the three pin plug, why doesn't it matter which way round the 'figure of eight ' connector is plugged in to the device?
Silverback

[Leif]

I would guess that your new stuff is double-insulated - Appliance classes - Wikipedia may shed more light on the matter.

[BobH]

Far be it from me to antagonize a silverback - I'm old and can no longer run fast enough, but are you certain that it is a figure of eight at the end? I frequently find that the end seems to be a figure of eight but on closer inspection one side is flat which means that it will connect only one way thus maintaining correct polarity.

[John Gray]

"Figure of 8" connectors with 180° rotational symmetry are quite common in the UK. Thank heaven we don't have the infuriating USB type A plugging problem with these!
I don't think I've ever come across one of the flat-sided plugs of which you speak...

[StuartR]

They are fairly common John, see for example https://duckduckgo.com/?q=figure+8+powe ... &ia=images

[BobH]

Yes, the pic is of the type to which I referred. I hadn't thought that it might be a US version. Notice the flat on the near side.

flat sided plug.jpg

[John Gray]

They are fairly common John, see for example https://duckduckgo.com/?q=figure+8+powe ... &ia=images

It shows what a sheltered life I've led!

[GeoffW]

It shows what a sheltered life I've led!

Or perhaps an insulated existence?

[silverback]

This is all well and good, people, but it doesn't answer my question. Bob's posting just reinforces my puzzlement. If the US puts a flat on one side of a figure of eight connector to make sure it 'goes in the right way', why doesn't it matter which way a UK figure of eight plug is inserted?
Silverback

[GeoffW]

Perhaps it's just a matter of manufacturing convenience for various products. Some products may require the flat connector, and some not - but the same cable can be used for all.

[DaveA]

Have a read at https://www.bhg.com/home-improvement/el ... polarized/ for polarized circuits here in the US.

Also for European sockets see https://toughleads.co.uk/pages/european-sockets

[Graeme]

Many appliances now don't require mains AC power so they have a power supply unit in them which is double insulated (as above) and the PSU outputs a DC voltage so the polarity isn't important because the PSU's rectifier ensures that both half cycles of the AC input are used as positive DC.

Regards

Graeme (Sparks R Us Ltd)