Power Supply Requirements...

[zzr1200]

The 13a plug on the table lamp should have a suitable size fuse to protect that cable. (Ie, 3a or 5a)

You can't do that with the blue industrial plugs as they don't have fuses.

I'm sure there are plenty of table lamps with 13a fuses fitted because a helpful son-in-law had fitted a new plug and left it with the fuse it was supplied with. Just waiting for granny to adjust the chair and fall asleep with a chair leg crushing the cable...

A quick Google suggests 7000 house fires a year with 89% being caused by electrical faults. Most common fault being an overloaded outlet followed by lamps and lighting..

I also don't disagree with you, I know mcb have type A/B/C/D power curves, which are for different initial rush draw currents for motors/transformers, so being as there are only a few countries that possibly use our system of wiring, and most others seem to use a system where each outlet is protected by a single mcb ie:- consumer unit mcb>cable>2/3 pin continental socket>a plug (no fuse)>cable>table lamp.

We'll agree to forget places like India where it's a free for all, Ratsnest system.....


Now my questions.........

Do the MCB Manufacturers make country specific mcb's or are all mcb made the same, and have a 30mA spec?

So why wouldn't a 32 amp mcb protect a circuit with a 16 amp item supplied by it, or is just the cables current capacity that controls the mcb rating.

I have in the past accidently cut a 1.5mm extension cable before, the mcb has tripped but the plug fuse was ok???

 

[Dave-sparks]

Do the MCB Manufacturers make country specific mcb's or are all mcb made the same, and have a 30mA spec?

MCBs don't have a 30mA spec, that is relevant to RCDs in all their forms. RCDs are commonly available in 10,30,100,300,500mA or variable, which tripping current you need depends on what type of protection you need.

MCBs are made to a few different standards internationally. In the UK we generally use MCBs made to two different standards BS/EN60898 (domestic use) and BS/EN60947 (non-domestic) which both have the B,C,D tripping curves but I think K and Z curves are only available in 60947 type.
These two standards are used across Europe and most other countries which follow regs or base their regs on ours.

MCBs used in the USA, and countries which use their NEC, are different and follow a different standard.

So why wouldn't a 32 amp mcb protect a circuit with a 16 amp item supplied by it, or is just the cables current capacity that controls the mcb rating.

Appliances should have their own protection built in and not rely on he installation they are supplied from to provide protection.
The MCB or fuse etc in the installation is there to protect the cables.

I have in the past accidently cut a 1.5mm extension cable before, the mcb has tripped but the plug fuse was ok???

Yes, that happens a lot. The answer is in something called selectivity between protective devices. Very basically the MCB reacted faster than the fuse.

 

[Dave-sparks]

What I was taught is that you choose the cable to match the max power requirements of the circuit and choose the MCB to protect that cable.

This is not the way it is done according to UK wiring regulations.

We work out how much current is needed, this is the design current (known as Ib)

Then we select the nominal current (In) which is the rating of the MCB to be used.

We then use this as the basis to calculate the size of cable required to operate safely.

 

[Buggerlugs]

I found this on the same type of box that my old Work zone 160Amp arc welder came in.

It could explain my previous confusion.