Protection and Features
•
Electronic thermal motor protection against overload.
•
Temperature monitoring of the heatsink ensures that the adjustable frequency drive trips if the temperature
reaches
203° F ± 10° F [95
°
C
±
5
°
C]. An overload temperature cannot be reset until the temperature of the heatsink is
below 158° F ± 10° F [70
°
C
±
5
°
C] (Guideline - these temperatures may vary for different power sizes, enclosures,
etc.). The adjustable frequency drive has an auto derating function to avoid its heatsink reaching 203° F [95
°
C].
•
The adjustable frequency drive is protected against short-circuits on motor terminals U, V, W.
•
If a line phase is missing, the adjustable frequency drive trips or issues a warning (depending on the load).
•
Monitoring of the intermediate circuit voltage ensures that the adjustable frequency drive trips if the intermediate
circuit voltage is too low or too high.
•
The adjustable frequency drive is protected against ground faults on motor terminals U, V, W.
10.3 Fuse Tables
10.3.1 Protection
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 short-circuited and
overcurrent protected according to national/international
regulations.
Short-circuit Protection:
The adjustable frequency drive 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 adjustable frequency drive. The adjustable
frequency drive 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 adjustable
frequency drive is equipped with 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.
Overcurrent protection must always be carried out
according to national regulations.
10.3.2 Fuse Selection
Danfoss recommends using the following fuses which will
ensure compliance with EN50178. In case of malfunction,
not following the recommendation may result in
unnecessary damage to the adjustable frequency drive.
The fuses below are suitable for use on a circuit capable of
delivering 100,000 Arms (symmetrical).
N90K-N250
380–500 V
type aR
N55K-N315
525–690 V
type aR
Table 10.5 Recommended Fuses
Specifications
VLT
®
Automation Drive D-Frame
Instruction Manual
10-8
MG34U222 - VLT
®
is a registered Danfoss trademark
10
10