Danfoss VLT AutomationDrive FC 300 Design Manual page 87

FC 300 Selection
4.6.4.3 Frame Size C, T7
60° AVM - Pulse Width Modulation
I out (A)
34
28.9
27.2
20.4
13.6
1 2 4
Illustration 4.33 Output current derating with switching
frequency and ambient temperature for frame size C2, 60° AVM.
Note: The graph is drawn with the current as absolute value and
is valid for both high and normal overload.
SFAVM - Stator Frequency Asyncron Vector Modulation
I (A)
out
100
86.6
80
66.6
60
45°C
40
50°C
20
55°C
1 2 4 6
Illustration 4.34 Output current derating with switching
frequency and ambient temperature for frame size C2, SFAVM.
Note: The graph is drawn with the current as absolute value and
is valid for both high and normal overload.
4.6.5 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.
The level of heating depends on the load on the motor, as
well as the operating speed and time.
Constant torque applications (CT mode)
A problem may occur at low RPM values in constant
torque applications. In a constant torque application s a
motor may over-heat at low speeds due to less cooling air
from the motor integral fan.
Therefore, if the motor is to be run continuously at an RPM
value lower than half of the rated value, the motor must
RSPSupply - 1-888-532-2706 - www.RSPSupply.com
http://www.RSPSupply.com/p-21462-Danfoss-131B8966-VLT-Automation-VT-Drive-VFD-FC301-230V-5-HP.aspx
®
VLT AutomationDrive FC 300 Design Guide, 0.25-75 kW
C2 all options
45°C
50°C
55°C
f sw (kHz)
6 8 10
C2 all options
f (kHz)
sw
8 10
®
MG33BE02 - VLT is a registered Danfoss trademark
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 puts a
limit to the motor size.
Variable (Quadratic) torque applications (VT)
In VT applications such as centrifugal pumps and fans,
where the torque is proportional to the square of the
speed and the power is proportional to the cube of the
speed, there is no need for additional cooling or de-rating
of the motor.
4.6.6 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
current (I ) should be derated in accordance with
out
Illustration 4.35.
Max.I (%)
out
at T
AMB, MAX
100%
91%
82%
1 km 2 km
Illustration 4.35 Derating of output current versus altitude at
T for frame sizes A, B and C. At altitudes above 2 km,
AMB, MAX
contact Danfoss 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 for a B-frame with T
= 50° C. At a temperature of 45° C (T
of the rated output current is available. At a temperature
of 41.7° C, 100% of the rated output current is available.
) or max. output
AMB
(K)
D T
AMB, MAX
at 100% I
out
B and C
A
enclosure
enclosure
0 K 0 K
-5 K -3.3 K
-9 K -6 K
3 km
Altitude (km)
AMB, MAX
- 3.3 K), 91%
AMB, MAX
85
4 4