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Furthermore, the terminal screw must be retightened after two days due to the softness of the aluminium. It is crucial to keep the connection a gas tight
joint, otherwise the aluminium surface will oxidize again.
5.3.7 Fuses
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 shortcircuit
and overcurrent protected according to the 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 in
tables 5.3 and 5.4 to protect service personnel or other equipment in case of an internal failure in the unit. The frequency converter provides full short
circuit protection in case of a short-circuit on the motor output.
Over-current protection:
Provide overload protection to avoid fire hazard due to overheating of the cables in the installation. Over current protection must always be carried out
according to national regulations. The frequency converter is equipped with an internal over current 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
rms
(symmetrical), 500 V/600 V maximum.
Non UL compliance:
If UL/cUL is not to be complied with, Danfoss recommends using the fuses mentioned in table 5.2, which will ensure compliance with EN50178:
In case of malfunction, not following the recommendation may result in unnecessary damage to the frequency converter.
Automation VT Drive FC322 Design Guide
5 How to Install
MG.20.X1.22 - VLT
®
is a registered Danfoss trademark
145
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