The all in one 230v plug in, combined plug and transformer that charges
mobile phones and the likes. A UK ring circuit depends on the plug having a
fuse in it (max 13A) or if it does not, the appliance is then protected to
maybe 32A at the CU MCB.
These wall chargers do not have fuses in them, putting the protection at say
32A at the MCB. Anyone know why? Is it because of the transformer wiring
is separated. The 230v winding is not touching the 12v winding? Anyone
know why the do not have a fuse in them?

Reply to
Doctor Drivel
The 230v and low voltage are indeed separate but the devices do have a fuse in them. It is usually a non resettable combination thermal and overcurrent fuse embedded in the primary winding wrapping.
Reply to
Peter Parry
On Fri, 2 Nov 2007 11:16:01 -0000, "Doctor Drivel" wrote:
The fuse in the plug is only to protect the cordset.
They have thermal protection. This permits the differentiation of power leaving the device in normal operation from power being dissipated in a defective transformer.
Reply to
Derek Geldard
In article ,
Sigh. The plug fuse is not to protect the ring but *solely* the flex to the appliance it feeds.
If the 230 volt winding was touching the 12 volt winding it would not be 12 volts now would it? Transformers are constructed using insulated wire for the windings.
The primary winding in the transformer of a wall wart has a non replacable thermal fuse built in to it. This will allow short term overloads of the secondary before rupturing. Regulated DC supplies usually incorporate electronic overload protection.
Reply to
Dave Plowman (News)
There are/were also a few warts with a wire link as a fuse and nowt else. I doubt they meet requirements for UK equipment, as there's no fire protection, but they exist. Probably imports from Oman or something.
Reply to
I think perhaps the OP has noticed that the transformer has split-bobbin construction and is not suggesting that transformers are wound from uninsulated wire...
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