Fuse

fuse it is a simple device protection electrical worker, in a position to interrupting the current flow if this exceeds one prefixed threshold.

Cartridge fuses

They are constituted from a generally cylindrical container, in or china, to whose inside is present a wire that joins two finishes them of contact. The thread is determine the proportions in such way to fuse (because of the heat produced for Joule effect) if the current that crosses it exceeds a value limit.
In the models for currents high the thread is dipped in sand, that it has the scope to extinguish quicklyvoltaico arc that R-all'.apertura of the circuit can be formed, and moreover the container is generally ceramic, for greater solidity.
If in the small fuses in glass integrity of the thread can be observed in transparency, in the opaque cartridges a mobile element is often present on a contact, withheld from the inner thread. If this is interrupted, the element pointer detaches itself or however it marks it the event.

Beyond that from the threshold of current in and the type of cartridge, the choice of a fuse is determined also from to be able of interruption and from the rapidity of participation. The models for the protection of systems electrical workers are in kind discs of a valve, in order sopportare short but intense the excess current produced from the starter of . Ultrafast models come instead employ to you in order to safeguard the delicate circuits to transistor.
Every fuse introduces one its curve characteristic, in which the time of participation it is function of the current.

The substitution of the fuses burns to you must be carried out with attention, possibly removing current to mount of the system, respecting the model originates them above all and trying to comprise the cause of the participation of protection.

Autoripristinanti fuses

In some particular situations where the short circuit or the overload can be frequent and in the norm, in order to avoid to replace the fuses frequently, particular models in a position to restoring itself automatically to stopping of the cause are used.
In practical they are constituted from one PTC (Positive Coefficient Temperatures) that is a resistore the whose value of it increases with the temperature. To the overcoming of a current value, the temperature increase cause a resistance increase, than in its turn cause an increase of the Joule effect and therefore via, with effect avalanche.