32 Planning – additional instructions
Selecting the fuses
There must be fuses both at the AC supply side of the drive and at the DC connection.
They protect the cabling and limit the drive damage in case of a short circuit.
Selecting the AC input fuses
Equip every drive which you connect to the AC power line with fuses. The default AC fuses
for each drive are given in the drive hardware manual. Obey these guidelines if you select
other fuses:
• Fuse type: Only use the default fuse types (aR, T, etc.). See the drive hardware
manual.
• Voltage rating: According to the drive AC voltage rating, except use 500 V fuses for the
380 … 500 V AC supply.
• Nominal current of the fuses I
F,N
≈ 1.6 × I
rec,ave
• I
rec,ave
is the average rectifying current of the drive.
• Factor 1.6 covers the influence of cyclic load and ambient conditions.
• If you do not know the average rectifier current of the drive, use the rated input
current of the drive instead. See the drive hardware manual.
• Make sure that the operation time of the fuse is below the limit given for the default
fuses. See the drive hardware manual.
Selecting the DC fuses
Equip every drive with DC fuses. Install a fuse on both DC+ and DC- cable that you
connect from the common DC link connection point to the drive.
Suitable fuses for each drive type are listed in section DC fuses on page 46. Obey these
guidelines if you select the fuses on your own:
• Fuse type: aR (ultra-rapid, fast)
• Voltage rating: Select according to the nominal DC voltage (U
DC
). See section DC
voltage limits of the drive on page 45.
• Nominal current: I
F,N
≈ 1.6 x I
dc,ave(i)
Make sure that the fuses also protect the DC cabling connected to the drive.
1.6 Factor which covers the influence of the cyclic load and ambient conditions
I
dc,ave
Average DC link current
I
F, N
Nominal current of the fuse
P
dc,ave(i)
Maximum average DC link power in the DC connection terminals of the
individual drive i. (during a worst case 3 min time window)
U
dc
actual DC link voltage = 1.35 x U
ac
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