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3 VLT Automation VT Drive Selection
3.5 Special Conditions
3.5.1 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.
3
3.5.2 Derating for Ambient Temperature
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 60 AVM or SFAVM in parameter 14-00.
A enclosures
60 AVM - Pulse Width Modulation
Illustration 3.1: Derating of I
for different T
for
out
AMB, MAX
enclosure A, using 60 AVM
In enclosure A, the length of the motor cable has a relatively high impact on the recommended derating. Therefore, the recommended derating for an
application with max. 10 m motor cable is also shown.
Illustration 3.3: Derating of I
for different T
for
out
AMB, MAX
enclosure A, using 60 AVM and maximum 10 m motor cable
72
MG.20.X1.22 - VLT
Remote Site Products - 1-888-532-2706 - www.remotesiteproducts.com
http://www.remotesiteproducts.com/p-20783-Danfoss-131X8145-VLT-Automation-VT-Drive-VFD-FC322-460V-.5-HP.aspx
Automation VT Drive FC322 Design Guide
).
AMB,MAX
SFAVM - Stator Frequency Asyncron Vector Modulation
Illustration 3.2: Derating of I
for different T
for
out
AMB, MAX
enclosure A, using SFAVM
Illustration 3.4: Derating of I
for different T
for
out
AMB, MAX
enclosure A, using SFAVM and maximum 10 m motor cable
®
is a registered Danfoss trademark
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