FC 300 Design Guide
FC 300 Selection
ventilation available determines the size of the torque that can be permitted under a continuous load.
If the motor is to run continuous ly at an RPM value lower than half the rated value, the motor must be
supplied w ith additional air for cooling (or use a mo tor designed for this type of operation).
Instead of s uch extra cooling, the load level of the motor can be reduced e.g. by choosing a larger
motor. However, the design of the adjustable frequency drive sets a limit to the motor size .
" Derating for Installing Long Motor Cables or
Cables with Larger Cross-Section
The max. cable length for FC 301 is 492 ft. [150 m] non-shielded cable and 164 ft. [50 m] shiel ded
cable,
respective for FC 302 is 984 ft. [300 m] non-shielded and 492 ft. [150 m] shield ed cable.
The ad justable freq u ency drive has been tested using 984 ft. [300 m] non-shielded
cable and 492 ft. [150 m] shielded cable.
The adjustable frequency drive has been designed to work using a motor cable with a rated
cross-section. If a cable with a larger cross-section is used, redu ce t
he output current
by 5% for every ste p the cross-section is increase d.
(Increased cable cross-se ction leads to increased capacity to ground, and thus
an increas ed ground leakage current).
" Temperature-Dependent Switch Frequency
This function ensures the highest possible switch
frequency without causing a thermal overload
of the adjustable freque ncy d r ive.
The internal
temperature indicates w h ether the switch frequency
canbebasedontheload,theambienttemperature,
the supply voltage, or the cable
length.
The switch f req u ency is set in par. 14-01.
69
MG.33.B6.22 - VLT is a registered Danfoss trademark
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