Danfoss VLT AQUA Drive Design Manual page 90

5. How to Install
Furthermore, the terminal screw must be retightened after two days due to the softness of the
aluminum. It is crucial to keep the connection a gas-tight joint, otherwise the aluminum surface
will oxidize again.
5.2.7. Fuses
Branch circuit protection:
In order to protect the installation against electrical and fire hazards, all branch circuits in an
installation, switch gear, machines, etc. must be protected from both short circuit and overcurrent
in accordance with national/international regulations.
Short circuit protection:
The adjustable frequency drive must be protected against short circuit in order to prevent electrical
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or fire hazard. Danfoss recommends using the fuses mentioned in tables 4.3 and 4.4 in order to
protect service personnel and equipment in case of an internal failure in the unit. The adjustable
frequency drive provides full short circuit protection in case of a short circuit in the motor output.
Overcurrent protection:
Provide overload protection to prevent fire hazard due to overheating of the cables in the instal-
lation. Overcurrent protection must always be provided according to national regulations. The
adjustable frequency drive is equipped with internal overcurrent protection that can be used for
upstream overload protection (UL applications excluded). See par. 4-18. Fuses must be designed
for protection in a circuit capable of supplying a maximum of 100,000 A
600 V maximum.
Non-UL compliance
If UL/cUL is not to be complied with, Danfoss recommends using the fuses mentioned in table
4.2, which will ensure compliance with EN50178:
In case of malfunction, not following the recommendation may result in unnecessary damage to
the adjustable frequency drive.
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MG.20.N2.22 - VLT ® is a registered Danfoss trademark.
VLT ® AQUA Drive Design Guide
(symmetrical), 500 V/
rms