implemented with circuitry as described in chapter
These circuits can
recognise a short circuit and safely turn off the IGBT. Should, nevertheless, the power
electronic components be destructed and, thus, a full short circuit occur, then the fuse
has to avoid consequential failures and limit the possible total damage.
Fuses are separated intodifferent groups. They are differentiated into:
Ultra rapid fuses
Semiconductor fuses formains (rectifier) diodes and thyristors (SCRs).
Fuses used inmedium- andhigh-voltage grids.
Fuses used in low-voltage grids.
Fuses built directly intoappliances.
The material of the insulating body of, for example, an NH fuse is traditionally made
from ceramics with a high content of aluminium oxide. This insulating body is filled with
quartz sand, which improves the cooling of the fusible link and quenches the arc when
the fuse blows. To minimise the resistance of the fuse the connectors are made from
copper with a silver or tin coating.
Exampleof anNH semiconductor fuse
Further differentiations are the two functional groups:
(partial section fuses)
Partial section fuses are those, which conduct current up to at least their
nominal value and can turn off currents above a certain multiple of their
nominal current, up to thenominal interrupt current.
(full section fuses)
Full section fuses are those, which conduct current up to at least their nominal
value and can turn off currents beginningwith the lowest melting current, up to
the nominal interrupt current.
Operating categories areanother classification. Thesedepend on theobjects toprotect: