Illustration 4.36: Derating of I
out
for different T
AMB, MAX
for Unit
Size 5x and 6x at 690 V, using 60º AVM in Normal torque mode
(110% over torque).
Illustration 4.37: Derating of I
out
for different T
AMB, MAX
for Unit
Size 5x and 6x at 690 V, using SFAVM in Normal torque mode
(110% over torque).
4.10.3 Derating for Low Air Pressure
The cooling capability of air is decreased at lower air pressure.
Below 1000 m altitude no derating is necessary but above 1000 m the ambient temperature (T
AMB
) or max. output current (I
out
) should be derated in accordance
with the shown diagram.
Illustration 4.38: Derating of output current versus altitude at T
AMB, MAX
for unit sizes 1x, 2x and 3x. At altitudes above 2 km, please contact GE regarding
PELV.
An alternative is to lower the ambient temperature at high altitudes and thereby ensure 100% output current at high altitudes. As an example of how to read the
graph, the situation at 2 km is elaborated. At a temperature of 45° C (T
AMB, MAX
- 3.3 K), 91% of the rated output current is available. At a temperature of 41.7° C,
100% of the rated output current is available.
Derating of output current versus altitude at T
AMB, MAX
for frame sizes 4x, 5x and 6x.
AF-650 GP Design Guide
87
4
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