3.3.5 Cooling Fans
All frequency converters in this size range are equipped
with cooling fans to provide airflow along the heatsinks
and within the enclosures. All fans are powered by mains
voltage which is stepped down by autotransformers and
regulated to 200 or 230 VAC by circuitry provided on the
power cards. On/off and high/low speed control of the
fans is provided to reduce overall acoustical noise and
extend the life of the fans.
Fans are activated by the following causes:
60% of nominal current exceeded
Specific heatsink temperature exceeded (power
size dependent)
Specific power card ambient temperature
exceeded
Specific control card ambient temperature
exceeded
DC hold active
DC brake active
Pre-magnetization of the motor
Automatic motor adaptation in progress
Regardless of the heatsink temperature, the fans
are started shortly after main input power is
applied to the frequency converter.
Once fans are started, they will run for a minimum of 10
minutes.
3.3.6 Fan Speed Control
The cooling fans are controlled with sensor feedback
which regulates fan operation and speed control as
described below.
•
IGBT thermal sensor measured temperature. The
fan can be off, low speed, or high speed based
on this temperature.
IGBT Thermal Sensor
Temperature
Fan turn ON low speed
45
°
C
Fan low speed to high speed
50
°
C
Fan high speed to low speed
40
°
C
Fan turn OFF from low speed
30
°
C
Table 3.1 IGBT Thermal Sensor
•
Power card ambient temperature sensor
measured temperature. The fan can be off or
high speed based on this temperature.
Power Card Ambient
Temperature
Fan turn ON to high speed
45
°
C
Fan turn OFF from high speed
40
°
C
Fan turn ON to high speed
<10
°
C
Table 3.2 Power Card Ambient Temperature Sensor
•
Control card thermal sensor measured
temperature. The fan can be off or low speed
based on this temperature.
Control Card Ambient
Temperature
Fan turn ON to low speed
55
°
C
Fan turn OFF from low speed
45
°
C
Table 3.3 Control Card Thermal Sensor
•
Output current value. If the output current is
greater than 60% of rated current, the fan will
turn on low speed.
3.3.7 Load Sharing
Units with the built-in load sharing option contain
terminals 89 (+) DC and 88 (-) DC. Within the frequency
converter, these terminals connect to the DC bus in front
of the DC link reactor and bus capacitors.
The use of the load sharing terminals can take on two
different configurations.
In one method, the terminals are used to tie the DC bus
circuits of multiple frequency converters together. This
allows for the possibility of one frequency converter that is
in a regenerative mode to share its excess bus voltage
with another frequency converter that is in motoring
mode. When applied correctly, this can reduce the need
for external dynamic brake resistors while also saving
energy. In theory, the number of frequency converters that
can be connected in this way is infinite; however, the
frequency converters must be of the same voltage rating.
In addition, depending on the size and number of
frequency converters, it may be necessary to install DC
reactors and DC fuses in the DC link connections and AC
reactors on the mains. Attempting such a configuration
requires specific considerations and should not be
attempted without first consulting Danfoss Application
Engineering.
In the second method, the frequency converter is powered
exclusively from a DC source. This is a bit more
complicated. First, a DC source is required. Second, a
means to soft charge the DC bus at power up is required.
Last, a mains voltage source is required to power the fans
within the frequency converter. Again such a configuration
should not be attempted without first consulting Danfoss
Application Engineering.
Internal Frequency Converte...
High Power Service Manual for Modular F Frame Drives
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®
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