Danfoss VLT AutomationDrive FC 300 Design Manual page 68

FC 300 Design Guide
Derating of I for different T
out
using 60 PWM in High torque mode (160% over torque)
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
max. output current (I
Derating of output current versus altitude at T
garding 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
ature of 41.7° C, 100% of the rated output current is available.
Derating for Running at Low Speed
When a motor is connected to a frequency converter, it is necessary to check that the cooling of the motor
is adequate.
A problem may occur at low RPM values in constant torque applications. The motor fan may not be able
to supply the required volume of air for cooling and this limits the torque that can be supported. There-
fore, if the motor is to be run continuously at an RPM value lower than half of the rated value, the motor
must be supplied with additional air-cooling (or a motor designed for this type of operation may be used).
An alternative is to reduce the load level of the motor by choosing a larger motor. However, the design
of the frequency converter puts a limit to the motor size.
Derating for Installing Long Motor Cables or Cables with Larger Cross-Section
The maximum cable length for FC 301 is 75 m unscreened and 50 m screened cable. For FC302 it is 300
m unscreened and 150 m screened
The frequency converter has been designed to work using a motor cable with a rated cross-section. If a
cable with a larger cross-section is used, reduce the output current by 5% for every step the cross-section
is increased.
68
FC 300 Selection
for enclosure C,
AMB, MAX
) should be derated in accordance with the shown diagram.
out
AMB, MAX
- 3.3 K), 91% of the rated output current is available. At a temper-
AMB, MAX
MG.33.B8.02 - VLT
Derating of I for different T
out
using SFAVM in High torque mode (160% over torque)
. By altitudes above 2 km, please contact Danfoss Drives re-
® is a registered Danfoss trademark
for enclosure C,
AMB, MAX
) or
AMB