Danfoss VLT AQUA Drive - Page 153

60 AVM - Pulse Width Modulation, 525 - 600 V
Illustration 10.17: Derating of I
out
for different T
AMB, MAX
for enclosure E
at 600 V, using 60 AVM in Normal torque mode (110% over torque).
SFAVM - Stator Frequency Asyncron Vector Modulation
Illustration 10.18: Derating of I
out
for different T
AMB, MAX
for enclosure E
at 600 V, using SFAVM in Normal torque mode (110% over torque).
10.2.3. Derating for Low Air Pressure
The cooling capability of air is decreased at lower air pressure.
At altitudes higher than 2 km, please contact regarding PELV.
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 10.19: Derating of output current versus altitude at T
AMB, MAX
. By altitudes above 2 km, please contact regarding PELV.
An alternative is to lower the ambient temperature at high altitudes and thereby ensure 100% output current at high altitudes.
10.2.4. 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. Therefore, 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.
VLT
®
AQUA Drive
Operating Instructions
10. Specifications
MG.20.M4.02 - VLT
®
is a registered Danfoss trademark 153
10