Automatic Adaptations To Ensure Performance; Derating For Low Air Pressure; Derating For Running At Low Speed - Danfoss FC 102 Design Manual

General Specifications and ...
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 9.23 Output current derating with switching
frequency and ambient temperature for enclosure typeC2,
SFAVM. Note: The graph is drawn with the current as absolute
value and is valid for both high and normal overload.
9.6.6 Automatic Adaptations to Ensure
Performance
The frequency converter constantly checks for critical levels
of internal temperature, load current, high voltage on the
intermediate circuit and low motor speeds. As a response
to a critical level, the frequency converter can adjust the
switching frequency and/or change the switching pattern
to ensure the performance of the frequency converter. The
capability for automatic output current reduction extends
the acceptable operating conditions even further.

9.6.7 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 the
out
following diagram.
Max.I (%)
out
at T
AMB, MAX
100%
91%
82%
1 km 2 km
Illustration 9.24 Derating of output current versus altitude at
T for enclosure types A, B and C. At altitudes above
AMB, MAX
2000 m, contact Danfoss regarding PELV.
MG11BC02
Design Guide
C2 all options
f (kHz)
sw
8 10
) 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)
Danfoss A/S © Rev. 06/2014 All rights reserved.
I (%)
OUT
100
95
90
85
80
0 500 1000 1500
Altitude (meters above sea level)*
Illustration 9.25 An alternative is to lower the ambient
temperature at high altitudes and thereby ensure 100%
output current at high altitudes
(°C)
45
40
35
30
0 500 1000 1500
Altitude (meters above sea level)*
Illustration 9.26 Example: At an altitude of 2000 m and a
temperature of 45 ° C (T
AMB, MAX
output current is available. At a temperature of 41.7 ° C, 100%
of the rated output current is available
Derating of output current versus altitude at T
enclosure types D, E and F.

9.6.8 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 applications, 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
be supplied with additional air-cooling (or a motor
designed for this type of operation may be used).
2000 2500 3000
HO
NO
2000 2500 3000
- 3.3 K), 91% of the rated
for
AMB, MAX
169
9 9