Danfoss FC 100, FC 200, FC 300 Application guide
Fuses and Circuit Breakers Application Note for FC 100, FC 200 and FC 300 Fuses and Circuit Breakers
1 Fuses and Circuit Breakers
1.1.1 Fuses
A frequency converter that works correctly limits the current
it can draw from the supply. Still, it is recommended to use
fuses and/ or Circuit Breakers on the supply side as
protection in case of component break-down inside the
frequency converter (first fault).
NOTE
This is mandatory in order to ensure compliance with IEC
60364 for CE or NEC 2009 for UL.
WARNING
Personnel and property must be protected against the
consequence of component break-down internally in the
frequency converter.
Branch Circuit Protection
In order to protect the installation against electrical and fire
hazard, all branch circuits in an installation, switch gear,
machines etc., must be protected against short-circuit and
over-current according to national/international regulations.
NOTE
The recommendations given do not cover Branch circuit
protection for UL!
1.1.2 Energy Required to Clearing the Circuit
It is important to choose a fuse/Circuit Breaker with a low I2t
2
s]. This parameter is the energy required to clearing and is
[A
a measure of the damaging effect on the frequency
converter.
Fuses offer better protection of the frequency converter than
Circuit Breakers as I
2
I
t
<< I2t
aR fuse
value
The fastest clearing is done with an aR fuse (partial range
accompanied protection for semiconductors) that is faster than
a gG fuse (wide-range general-purpose protection for cables,
conductors and wires). Circuit Breakers are slower.
2
t is smaller for fuses.
<< I2t
gG fuse
circuit breaker
for the same nominal
1.1.3 Safely Breaking the Current
Fuses and Circuit Breakers must be capable of safely
breaking the current in the event of a short circuit. When a
large electric current is interrupted an arc may form and if
the breaking capacity of a fuse or circuit breaker is exceeded
then it may not be able to extinguish this arc and the current
will continue, which might have severe consequences.
1 1
Short-circuit protection:
Danfoss recommends using the fuses/Circuit Breakers listed
in 1.1.6 CE Compliance and 1.1.7 UL Compliance to protect
service personnel and property in case of component breakdown in the frequency converter.
Over current protection:
The frequency converter provides overload protection to
limit threats to human life, property damage and to avoid
fire hazard due to overheating of the cables in the installation. The frequency converter is equipped with an internal
over current protection (4-18 Current Limit) that can be used
for upstream overload protection (UL-applications excluded).
Moreover, fuses or Circuit Breakers can be used to provide
the over current protection in the installation. Over current
protection must always be carried out according to national
regulations.
This breaking capacity is known as the Short Circuit Current
Rating (SCCR).
The prospective short circuit current (PSCC) is the highest
electric current which can exist in a particular electrical
system under short circuit- and ground fault conditions and
is determined by the voltage and impedance of the supply
system.
With gG fuses, the SCCR is 100 kA rms (symmetrical) which
means that it will be possible to disconnect a PSCC of up to
100 kA rms (symmetrical). The recommended aR fuses and
Circuit Breakers have a lower SCCR which means that they
will not be able to disconnect a PSCC of that magnitude. The
data sheets must be consulted for details.
NOTE
In general, be aware that your fuse/Circuit Breaker must be
capable of handling the PSCC.
MN.90.T1.02 - VLT® is a protected Danfoss trademark 1
Fuses and Circuit Breakers Application Note for FC 100, FC 200 and FC 300 Fuses and Circuit Breakers
1
1.1.4 Fuses and Circuit Breakers
The selection of fuse and/or Circuit Breaker will depend on
preferences and on the installation in question. Sometimes it
is necessary to combine the two.
Fuses
A nonrenewable fuse interrupts excessive current by
clearing. Fuses are selected to allow passage of normal
current and of excessive current only for short periods. After
clearing, the fuse must be replaced.
gG-fuses offer full protection and can be used alone or as
electrical branch-fuse.
NOTE
aR semi-conductor fuses must never be used as the only
protection. Always combine with gG fuses or a Circuit
Breaker depending on the prospective current.
Alternatively, gRL fuses can be used alone.
Circuit Breakers
A Circuit Breaker is an automatically-operated electrical
switch that is designed for overload protection. It can be
used to interrupt excessive current by disconnecting but it is
slower than a nonrenewable fuse. Unlike a fuse, which
operates once and then has to be replaced, a circuit breaker
can be reset (either manually or automatically) to resume
normal operation. When a current is interrupted, an arc is
generated. Different techniques are used to extinguish the
arc.
NOTE
Circuit Breakers should generally not be used as the only
protection. There are some Circuit Breakers now, however,
that can do the job. Generally, combine with a gG fuse or a
bigger Circuit Breaker branch-fuse for the desired protection
depending on the prospective current.
Illustration 1.2 Circuit Breakers should Generally not be used as the
Only Protection
Illustration 1.1 gG Fuses offer Full Protection and can be Used
Alone or as Electrical Branch-fuse
2 MN.90.T1.02 - VLT® is a protected Danfoss trademark
Fuses and Circuit Breakers Application Note for FC 100, FC 200 and FC 300 Fuses and Circuit Breakers
1.1.5 Recommendations
WARNING
In case of malfunction, not following the recommendation
may result in personnel risk and damage to the frequency
converter and other equipment.
The following tables list the recommended rated current.
Recommended fuses are of the type gG for small to medium
power sizes. For larger powers, aR fuses are recommended.
For Circuit Breakers, Moeller types have been tested to have
a recommendation. Other types of circuit breakers may be
used provided they limit the energy into the drive to a level
equal to or lower than the Moeller types.
If fuses/Circuit Breakers according to recommendations are
chosen, possible damages on the frequency converter will
mainly be limited to damages inside the unit.
NOTE
Following the recommendations puts the direct fuses/Circuit
Breaker in place (a, b, c... in figure below). It does NOT make
up for considering combined protection or branch circuit
protection (see x in illustration below).
1 1
NOTE
The dimensions in Table 1.2 are for an ambient temperature
at 20C. At an ambient temperature at 40C, use Recommended
Max. fuse for gR/aR.
MN.90.T1.02 - VLT® is a protected Danfoss trademark 3
Fuses and Circuit Breakers Application Note for FC 100, FC 200 and FC 300 Fuses and Circuit Breakers
1
1.1.6 CE Compliance
Fuses or Circuit Breakers are mandatory to comply with IEC 60364. Danfoss recommend using a selection of the following.
The fuses below are suitable for use on a circuit capable of delivering 100,000 Arms (symmetrical), 240V, or 480V, or 500V, or
600V depending on the drive voltage rating. With the proper fusing the drive short circuit current rating (SCCR) is 100,000
Arms.
Enclosure FC 300 Power FC 100/200
Power
Size [kW] [kW] Moeller [A]
A1 0.25-1.5 - gG-10 gG-25 PKZM0-16 16
A2 0.25-2.2 0.25-2.2 gG-10 (0.25-1.5)
A3 3.0-3.7 3.0-3.7 gG-16 (3)
B3 5.5 5.5-11 gG-25 gG-63 PKZM4-50 50
B4 7.5-15 15-18 gG-32 (7.5)
C3 18.5-22 22-30 gG-80 (18.5)
C4 30-37 37-45 aR-160 (30)
A4 0.25-2.2 0.25-2.2 gG-10 (0.25-1.5)
A5 0.25-3.7 0.25-3.7 gG-10 (0.25-1.5)
B1 5.5-7.5 5.5-11 gG-25 (5.5)
B2 11 15 gG-50 gG-100 NZMB1-A100 100
C1 15-22 18.5-30 gG-63 (15)
C2 30-37 37-45 aR-160 (30)
Recommended
fuse size
gG-16 (2.2)
gG-20 (3.7)
gG-50 (11)
gG-63 (15)
aR-125 (22)
aR-200 (37)
gG-16 (2.2)
gG-16 (2.2-3)
gG-20 (3.7)
gG-32 (7.5)
gG-80 (18.5)
gG-100 (22)
aR-200 (37)
Recommended
Max. fuse
gG-25 PKZM0-25 25
gG-32 PKZM0-25 25
gG-125 NZMB1-A100 100
gG-150 (18.5)
aR-160 (22)
aR-200 (30)
aR-250 (37)
gG-32 PKZM0-25 25
gG-32 PKZM0-25 25
gG-80 PKZM4-63 63
gG-160 (15-18.5)
aR-160 (22)
aR-200 (30)
aR-250 (37)
Recommended
circuit breaker
NZMB2-A200 150
NZMB2-A250 250
NZMB2-A200 160
NZMB2-A250 250
Max trip level
Table 1.1 200-240V, Frame Sizes A, B, and C
4 MN.90.T1.02 - VLT® is a protected Danfoss trademark
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