Derating For Installing Long Motor Cables Or Cables With Larger Cross-Section; Temperature-Dependent Switch Frequency - Danfoss VLT AutomationDrive FC 300 Design Manual

FC 300 Design Guide
Instead of utilizing 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 adjustable frequency drive has been tested using 1000 ft (300 m) non-shielded
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-section is used, reduce the output current
by 5% for every step the cross-section is increased.
(Increased cable cross-section leads to increased capacity to ground, and thus
an increased ground leakage current).

Temperature-Dependent Switch Frequency

"
This function ensures the highest possible switch
frequency without causing a thermal overload
of the adjustable frequency drive. The internal
temperature indicates whether the switch frequency
can be based on the load, the ambient temperature,
the supply voltage, and the cable length.
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