FC 300 Design Guide
How to Select Your VLT
Instead of utilizing extra cooling, the load level of the motor can be reduced e.g. b y choosing a larg er
motor, however, the design of the adjustable freque n cy drive sets a limit to the motor size.
" Derating for Install in g Long Motor Cables or
Cables with Larger Cross-Section
The ad jus table frequency drive has been tested usi ng 1000 ft (300 m) non-shielde d
cable and 500 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-se ction is used, reduce the o utp u t current
by 5% for every ste p the cross-section is increase d.
(Increased cable cross-se ction leads to increased cap acity to ground, and thus
an increas ed ground leakage current).
" Temperature-Dependent Switch Frequency
This function ensures the highest possible switch
frequency w ithout causing a thermal overload
of the adjustable frequency drive. The internal
temperature indicates whether the switch
frequency
canbebasedontheload,theambienttemperature,
the supply voltage, and the cable length.
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MG.33.B3.22 - VLT is a registered Danfoss trademark
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