Special Conditions - Danfoss FC 300 Design Manual

FC 300 Design Guide

4.9 Special Conditions

4.9.1 Purpose of Derating
Derating must be taken into account when using the frequency converter at low air pressure (heights), at low speeds, with long motor cables, cables
with a large cross section or at high ambient temperature. The required action is described in this section.
4.9.2 Derating for Ambient Temperature and IGBT Switching Frequency
The average temperature (T ) measured over 24 hours must be at least 5 °C lower than the maximum allowed ambient temperature (T
AMB, AVG
If the frequency converter is operated at high ambient temperatures, the continuous output current should be decreased.
The derating depends on the switching pattern, which can be set to 60º AVM or SFAVM in par. 14-00
Frame size A
60º AVM - Pulse Width Modulation
Illustration 4.2: Derating of I
frame size A, using 60º AVM
When using only 10 m motor cable or less in frame size A, less derating is necessary. This is due to the fact that the length of the motor cable has a
relatively high impact on the recommended derating.
Illustration 4.4: Derating of I
frame size A, using 60º AVM and maximum 10 m motor ca-
ble
for different T for
out AMB, MAX
for different T for
out AMB, MAX
MG.33.BC.02 - VLT ® is a registered Danfoss trademark
4 AutomationDrive FC 300 Selection
Switching Pattern
SFAVM - Stator Frequency Asyncron Vector Modulation
Illustration 4.3: Derating of I
frame size A, using SFAVM
Illustration 4.5: Derating of I
frame size A, using SFAVM and maximum 10 m motor cable
).
AMB,MAX
.
for different T for
out AMB, MAX
for different T for
out AMB, MAX
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