Danfoss VLT Series Design Manual page 100

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 - the 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 avoid electrical
5
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 avoid fire hazard due to overheating of the cables in the installation.
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
4-18
100,000 A
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.
100
. Fuses must be designed for protection in a circuit capable of supplying a maximum of
(symmetrical), 500 V / 600 V maximum.
rms
MG.11.B4.22 - VLT
®
VLT HVAC Drive Programming Guide, par.
® is a registered Danfoss trademark.
VLT ® HVAC Drive Design Guide