1.9 Special Conditions
1.9.1 Derating for Ambient Temperature
The ambient temperature measured over 24 hours should
be at least 9° F [5°C] lower than the max. ambient
temperature.
If the adjustable frequency drive is operated at a high
ambient temperature, the continuous output current
should be decreased.
The adjustable frequency drive has been designed for
operation at max 122° F [50°C] ambient temperature with
one motor size smaller than nominal. Continuous
operation at full load at 122° F [50°C] ambient temperature
will reduce the lifetime of the adjustable frequency drive.
1.9.2
Derating for Low Air Pressure
The cooling capability of air is decreased at low air
pressure.
For altitudes above 6,600 feet [2 km], contact Danfoss
regarding PELV.
Below altitudes of 3,300 ft [1,000 m], no derating is
necessary, but at 3,300 ft [1,000 m] and higher, the
ambient temperature or maximum output current should
be decreased.
Decrease the output by 1% per 328 ft [100 m] higher than
an altitude of 3,300 ft [1,000 m], or reduce the max.
ambient temperature by 1 degree per 656 ft [200 m].
1.9.3 Derating for Running at Low Speeds
When a motor is connected to an adjustable frequency
drive, it is necessary to make sure that the cooling of the
motor is adequate.
A problem may occur at low speeds in constant torque
applications. Running continuously at low speeds – below
half the nominal motor speed – may require additional air
cooling. Alternatively, choose a larger motor (one size up).
Quick Guide
VLT
®
Micro Drive Quick Guide
1-22 MG02B722 - VLT
®
is a registered Danfoss trademark
11
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