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 prevent electrical 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 in

accordance with 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

(symmetrical), 500 V/600 V maximum.

rms

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.

5-2

Figure 5.4: Cable entry holes for enclosure C2. The sugges-

ted use of the holes are purely recommendations, and other

solutions are possible.