Danfoss FC 300 Design Manual page 53

FC 300 Design Guide
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The control unit may attempt to correct the ramp if possible (par. 2-17
The inverter turns off to protect the transistors and the intermediate circuit capacitors when a
certain voltage level is reached.
See par. 2-10 and par. 2-17 to select the method used for controlling the intermediate circuit
voltage level.
Line Drop-out
During a line drop-out, the adjustable frequency drive keeps running until the intermediate circuit
voltage drops below the minimum stop level, which is typically 15% below the adjustable fre-
quency drive's lowest rated supply voltage.
The line voltage before the drop-out and the motor load determine how long it takes for the
inverter to coast.
Static Overload in VVCplus mode
When the adjustable frequency drive is overloaded (the torque limit in par. 4-16/4-17 is reached),
the control reduces the output frequency to reduce the load.
If the overload is excessive, a current may occur that makes the adjustable frequency drive cut
out after approximately 5-10 s.
Operation within the torque limit is limited in time (0-60 s) in par. 14-25.
3.10.1. Motor Thermal Protection
The motor temperature is calculated on the basis of motor current, output frequency, and time
or thermistor. See par. 1-90 in the Programming Guide.
The load drives the motor (at constant output frequency from the adjustable frequency
drive), i.e., the load generates energy.
During deceleration ("ramp-down"), if the moment of inertia is high the friction is low
and the ramp-down time is too short for the energy to be dissipated as a loss in the
adjustable frequency drive, the motor and the installation.
Incorrect slip compensation setting may cause higher DC link voltage.
MG.33.B9.22 - VLT ® is a registered Danfoss trademark.
3. Introduction to FC 300
Overvoltage Control
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