Danfoss VLT HVAC Drive FC 100 Series, Руководство по конструкции

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situation at 6,500 ft [2 km] is elaborated. At a temperature
of 113°F [45
°
C] (T
AMB, MAX
- 3.3 K), 91% of the rated output
current is available. At a temperature of 107°F [41.7
°
C],
100% of the rated output current is available.
80
0 500
100
95
90
85
1000 1500 2000 2500 3000
Altitude (meters above sea level)*
130BB008.10
I
OUT
(%)
Figure 8.4
0 500 1000 1500 2000 2500 3000
Altitude (meters above sea level)*
30
35
40
45
(°C)
A
mb
. T
emp
.
130BB009.10
HO
NO
Figure 8.5
Derating of output current versus altitude at T
AMB, MAX
for
frame sizes D, E and F.
8.6.5 Derating for Running at Low Speed
When a motor is connected to a Adjustable frequency
drive, it is necessary to make sure 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, a
motor may overheat 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).
An alternative is to reduce the load level of the motor by
choosing a larger motor. However, the design of the
Adjustable frequency drive 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.
In the graphs shown below, the typical VT curve is below
the maximum torque with de-rating and maximum torque
with forced cooling at all speeds.
Maximum load for a standard motor at 40
°
C driven by a
Adjustable frequency drive type VLT FCxxx
10 20 30 40 50 60 70 80 90 100 110
20
40
60
80
100
120
0
v %
T %
0
1)
130BA893.10
Legend:
─ ─ ─ ─
Typical torque at VT load
─•─•─•─
Max torque
with forced cooling
‒‒‒‒‒
Max torque
Note 1) Oversynchronous speed operation will result in the
available motor torque decreasing inversely proportional to the
increase in speed. This must be considered during the design
phase to avoid overloading the motor.
Table 8.43
8.7 Troubleshooting
A warning or an alarm is signaled by the relevant LED on
the front of the Adjustable frequency drive and indicated
by a code on the display.
A warning remains active until its cause is no longer
present. Under certain circumstances operation of the
motor may still be continued. Warning messages may be
critical, but are not necessarily so.
General Specifications and ...
VLT
®
HVAC Drive Design Guide
8-28 MG11BB22 - VLT
®
is a registered Danfoss trademark
8 8