Protection and Features
•
Electronic thermal motor protection against overload.
•
Temperature monitoring of the heat sink ensures that the frequency converter trips if the temperature reaches
95
°
C
±
5
°
C. An overload temperature cannot be reset until the temperature of the heat sink is below 70
°
C
±
5
°
C
(Guideline - these temperatures may vary for different power sizes, enclosures etc.). The frequency converter has
an auto derating function to avoid its heat sink reaching 95
°
C.
•
The frequency converter is protected against short-circuits on motor terminals U, V, W.
•
If a mains phase is missing, the frequency converter trips or issues a warning (depending on the load).
•
Monitoring of the intermediate circuit voltage ensures that the frequency converter trips if the intermediate circuit
voltage is too low or too high.
•
The frequency converter is protected against ground faults on motor terminals U, V, W.
11.3 Fuse Tables
11.3.1 Protection
Branch circuit protection
To protect the installation against electrical and fire hazard,
all branch circuits in an installation, switch gear, machines
etc., must be short-circuited and over-current protected
according to national/international regulations.
Short-circuit protection
The frequency converter must be protected against short-
circuit to avoid electrical or fire hazard. Danfoss
recommends using the fuses mentioned below to protect
service personnel and equipment in case of an internal
failure in the frequency converter. The frequency converter
provides full short-circuit protection in case of a short-
circuit on the motor output.
Overcurrent protection
Provide overload protection to avoid fire hazard due to
overheating of the cables in the installation. The frequency
converter is equipped with an internal overcurrent
protection that can be used for upstream overload
protection (UL-applications excluded). See
4-18 Current
Limit
. Moreover, fuses or circuit breakers can be used to
provide the overcurrent protection in the installation. Over-
current protection must always be carried out according to
national regulations.
11.3.2 Fuse Selection
Non-UL compliance
Danfoss recommends using the following fuses, which
ensure compliance with EN 50178. In case of malfunction,
not following the recommendation may result in
unnecessary damage to the frequency converter.
N110-N315
380–480 V
type aR
N75K–N400
525–690 V
type aR
P355-P450
380–480 V
type gG
Table 11.4 EN50178 Fuses
UL compliance
The fuses below are suitable for use on a circuit capable of
delivering 100000 A
rms
(symmetrical). With the proper
fusing, the frequency converter Short Circuit Current Rating
(SCCR) is 100000 A
rms
.
Specifications
Operating Instructions
102
Danfoss A/S © Rev. 05/2014 All rights reserved.
MG16J202
11
11
Summary of Contents for VLT FC 103
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