10.2 Special Conditions
10.2.1 Purpose of derating
Derating must be taken into account when using the adjustable frequency drive at low air pressure (high elevations), 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.
10.2.2 Derating for Ambient Temperature
The average temperature (T
AMB, AVG
) measured over 24 hours must be at least 9°F [5°C] lower than the maximum allowed ambient temperature
(T
AMB,MAX
).
If the adjustable frequency drive 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
Figure 10.1: Derating of I
out
for different T
AMB, MAX
for en-
closure A, using 60 AVM
SFAVM - Stator Frequency Asyncron Vector Modulation
Figure 10.2: Derating of I
out
for different T
AMB, MAX
for en-
closure A, using SFAVM
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. 32 ft [10 m] motor cable is also shown.
Figure 10.3: Derating of I
out
for different T
AMB, MAX
for en-
closure A, using 60 AVM and maximum 32 ft [10 m] motor
cable
Figure 10.4: Derating of I
out
for different T
AMB, MAX
for en-
closure A, using SFAVM and a maximum of 32 ft [10 m]
motor cable
VLT
®
AQUA Drive
Instruction Manual
10 Specifications
MG.20.M5.22 - VLT
®
is a registered Danfoss trademark
10-17
10