Danfoss VLT Instruction Manual page 172

8 Specifications
8.2 Special Conditions
8.2.1 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.
8.2.2 Derating for Ambient Temperature
90% adjustable frequency drive output current can be maintained up to a max. of 122°F [50°C] ambient temperature.
With a typical full load current of EFF 2 motors, full output shaft power can be maintained up to 122°F [50°C].
For more specific data and/or derating information for other motors or conditions, please contact Danfoss.
8.2.3 Automatic adaptations to ensure performance
The adjustable frequency drive constantly checks for critical internal temperature levels, load current, high voltage on the intermediate circuit and low
motor speeds. As a response to a critical level, the adjustable frequency drive can adjust the switching frequency and / or change the switching pattern
in order to ensure the performance of the adjustable frequency drive. The capability to automatically reduce the output current extends the acceptable
operating conditions even further.
8
8.2.4 Derating for Low Air Pressure
The cooling capability of air is decreased at a lower air pressure.
At altitudes higher than 6,600 feet [2 km], please contact Danfoss regarding PELV.
At an altitude lower than 3,280 ft [1,000 m], no derating is necessary, but above 3,280 ft [1,000 m], the ambient temperature (T
current (I ) should be derated in accordance with the diagram shown.
out
Figure 8.1: Derating of output current versus altitude at T
PELV.
An alternative is to lower the ambient temperature at high altitudes and thereby ensure 100% output current at high altitudes.
8-20
. At altitudes above 6,600 feet [2 km], please contact Danfoss regarding
AMB, MAX
MG.11.A9.22 - VLT ® is a registered Danfoss trademark
VLT ® HVAC Drive Instruction Manual
) or max. output
AMB