Socomec UL General Catalog

Fuse solutions: definite advantages
over circuit breakers
Fusible
disconnect switches
fuser_185_e_gb
Fuses: a high performance
kA
Fuse
Prospective
short circuit
current
time
ms
Due to the high current limiting
CC, J and L type fuses, the best
protection will be provided to
downstream components, such as
motor or motor starter.
Our disconnects have been
designed around this concept to
provide 200kA as a SCCR on
most of the range.
fuser 192 b
Safety
The energy released during a short-circuit is
contained in the sealed fuse cartridge, there is
no release of ionized gases, thus no effect on
surrounding equipment in comparison to what
happens when circuit-breakers open on shortcircuit.
fuser 487 a gb
Circuit-breakers:
reduced breaking capacity
Current kA
Circuit breaker
Fuse
Voltage
Breaking capacity of circuitbreakers
reduces dramatically
when voltage increases: capacity
can decrease from 100kA at
240V to 20kA or even less at
600 V.
fuser 490 d gb
Reliability over time
Reliability
Circuit breaker
Fuse
Time
Fuses are totally sealed
products, which guarantee longterm
protection without any
maintenance.
Circuit-breakers are complex
devices including lots of moving
parts. Their mechanism is affected
by dust, humidity… and needs
maintenance.
fuser 664 a
Re-close or Replace ?
Circuit-breakers can be re-closed after
a default: that’s the biggest argument of
their manufacturers.
You should however consider that the
circuit-breaker should be inspected each
time there is a significant short-circuit.
It is hard to know how many times a
circuit-breaker has operated…
In contrast, when a fuse blows, it is
replaced by a new one, and the installation
is as relia ble as prior to the fault.
Thus, Re-close or replace ?
fuser 610 a
Last longer
Our FUSERBLOC show 2 main
functionalities:
magneto-thermal protection, made
inside the encapsulated fuses,
disconnection thru moving contacts
that stay closed during short-circuit
(arc won’t destroy them).
On a circuit-breaker both functionality
are on the same mechanical element.
Evolution of NEC ® regulation
Requirement of panel sccr
Art 409 of NEC ® 2005 & UL 508A
According to NEC ® 2005, all industrial control panels must be
marked with a Short-Circuit Current Rating (SCCR).
This covers the entire panel and not just the primary rating of the
over-current protection device, as commonly done before.
Calculation of this Panel SCCR is easy with Fuse Disconnect
Switch, since there is a defined table SB4.1 in UL 508 which
specifies Ip (peak value) of feeder fuse that can be used for
protection of downstream components, which is not the case on
circuit-breakers. Thanks to the high current limiting characteristics
of the fuses the SCCR of brauch circuits can be highly enhanced.
Arc flash NEC ® 2005
The NEC now contains requirements related to arc flash
hazards. Section 110-16, Flash Protection, requires markings on
switchboard, panel boards, industrial control panels and motor
control centers to warn from potential arc flash hazards.
Arc flash mitigation is greatly enhanced by the use of fuses and
their current limiting capabilities and fast opening times.
92 General Catalog UL/CSA Ed. 2