3.3.5 Cooling Fans
All adjustable frequency drives in this size range are
equipped with cooling fans to provide airflow along the
heatsink. Units in IP21 (NEMA 1) and IP54 (NEMA 12)
enclosures have a fan mounted in the enclosure door to
provide more airflow to the unit. IP20 enclosures have a
fan mounted to the top of the unit for more cooling. There
is a small 24 V DC mixing fan mounted under the input
plate. This fan operates any time the adjustable frequency
drive is powered on.
All fans run on DC voltage from the power card. The
mixing fan is powered by 24 V DC from the main switch
mode power supply. The heatsink fan and the door/top
fan are powered by 48 V DC from a dedicated switch
mode power supply on the power card. Each fan has
tachometer feedback to the control card to confirm that
the fan is operating correctly. On/off and speed control of
the fans is provided to reduce overall acoustical noise and
extend the life of the fans.
The following conditions activate the fans:
•
Output current greater than 60% of nominal
•
High IGBT temperature
•
Low IGBT temperature
•
High control card temperature
•
DC hold active
•
DC brake active
•
Dynamic brake circuit active
•
During pre-magnetization of the motor
•
AMA in progress
In addition to these conditions, the fans are always started
shortly after line input power is applied to the adjustable
frequency drive. Once fans are started, they run for a
minimum of one minute.
3.3.6 Fan Speed Control
The following conditions cause the fans to run at full
speed:
•
Low IGBT temperature
•
Active DC hold
•
Active DC brake
•
Active dynamic brake circuit
•
Pre-magnetization of the motor
•
AMA in progress
Mixing Fan
The mixing fan runs at full speed whenever the adjustable
frequency drive has power.
Heatsink Fan
The IGBT temperature and the output current determine
the speed of the heatsink fan. That fan runs at the higher
of the two settings.
If the output is greater than 60% of the nominal current,
the fan runs at 100% speed. If the output current is less
than 60% of the nominal current, the fan turns off.
When the IGBT temperature reaches the fan turn on
temperature, the fan starts and runs at its minimum speed.
As the IGBT temperature increases, the fan speed increases.
When the IGBT temperature reaches the fan maximum
speed temperature, the fan is running at 100% speed. As
the IGBT temperature decreases, the fan speed decreases.
The fan stops running when the IGBT temperature falls
below the fan turn off temperature.
•
Fan turn on temperature = 104°F [40°C]
•
Fan minimum speed temperature = 104°F [40°C]
•
Fan maximum speed temperature = 176°F [80°C]
•
Fan turn off temperature = 104°F [40°C]
Door/Top Fan
The control card temperature, the IGBT temperature, and
the output current determine the speed of the door/top
fan. The fan runs at the highest of the three settings.
If the output is greater than 60% of the nominal current,
the fan runs at 100% speed. If the output current is less
than 60% of the nominal current, the fan is turned off.
Internal Adjustable Frequen...
Service Manual
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Danfoss A/S © Rev. 2014-02-10 All rights reserved.
MG94A222
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Summary of Contents for VLT FC 103
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