Danfoss VLT HVAC FC 100, Руководство по обслуживанию, Страница: 56 / 220

Power Card Ambient D Frame Units E Frame Units
Fan turn on to High Speed 95°F [35 ° C] 113°F [45 ° C]
Fan turn off from High Speed 86°F [30 ° C] 104°F [40 ° C]
Fan turn on to High Speed
<50°F [<10
°
C] <50°F [<10
°
C]
Table 3.2: Power Card Ambient Temperature Sensor
3. Control card thermal sensor measured temperature. The fan can be off or low speed
based on this temperature.
Control Card Ambient D Frame Units E Frame Units
Fan turn on to Low Speed 131°F [55 ° C] 131°F [55 ° C]
Fan turn off from Low Speed 113°F [45 ° C] 113°F [45 ° C]
Table 3.3: Control Card Thermal Sensor
4. 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
adjustable frequency drive, 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 adjustable frequency
drives together. This allows for the possibility of one adjustable frequency drive that is in a re-
generative mode to share its excess bus voltage with another adjustable frequency drive 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 adjustable frequency drives that can
be connected in this way is infinite; however, the adjustable frequency drives must be of the same
voltage rating. In addition, depending on the size and number of adjustable frequency drives, it
may be necessary to install DC reactors and DC fuses in the DC link connections and AC reactors
on line power. Attempting such a configuration requires specific considerations and should not be
attempted without first consulting Danfoss Application Engineering.
In the second method, the adjustable frequency drive 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, an AC line voltage source is required to power the fans
within the adjustable frequency drive. Again such a configuration should not be attempted without
first consulting Danfoss Application Engineering.
High Power Service Manual for VLT
®
FC Series
Adjustable Frequency Drives
3 Internal Adjustable Frequency Drive Opera-
tion
MG.90.L1.22 - VLT ® is a registered Danfoss trademark
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