4.4.8 1282250000 2012/2013
.Definition overload and short-circuit protection
Power losses
This technical supplement should be
used for determining the size fuse
inserts and fuse terminal blocks.
The heat generated when fuse insert
is activated short circuit low in
comparison overload.43 and 384. Definition overload and
short-circuit protection
a) Short-circuit protection
Short circuits can occur when the
insulation broken when there is
continued stress the insulating
material.
Figure Fuse terminal blocks
arranged individually
The maximum power loss the fuse
can, comparison compound
alignment, rated higher because the
individually aligned feed-through
terminals dissipate little thermal
energy.
Overload currents can occur with the
following electrical components:
• Cables and busbars power
distribution networks
• Motors
• Transformers
When protecting against overloads, the
heat energy released the fuse inserts
extends over longer period time.
Thus the maximum power loss less
than with pure short circuit. Fuse terminal blocks arranged
individually accordance with
IEC 60947-7-3
A single arrangement describes a
terminal block consisting five
terminals, whereby four feed-through
terminals are arranged around fuse
terminal block. Composite alignment fuse
terminal blocks accordance
with IEC 60947-7-3
A composite alignment describes a
terminal block made from five fuse
terminal blocks. also
shows the maximum permitted power
losses for the fuse inserts various
applications and terminal block
alignments.
W
Technicalappendix
W. The fuse
terminal blocks arranged a
composite dissipate more thermal
energy during operations. the case pure
short circuit, the maximum permitted
power loss the fuse insert should be
higher than the level for the overload
protection.473 S1.
3.
b) Overload protection
With overload protection, cables and
electrical components are protected
against excessive load currents and the
resulting thermal and mechanical
damages. This is
because only short pulse occurs with
a short circuit.
Figure Fuse terminal blocks
arranged composites
The maximum power loss the fuse
should, comparison the individual
alignment, rated lower.
1. The power loss for a
short circuit overload determined
based the terminal the middle. Almost all electrical
consumers and lines should be
protected against short circuits
according DIN VDE 0100-430/ HD
384.
2
