Motor Thermal Protection; Safe Stop Operation (Fc 302 Only) - Danfoss VLT AutomationDrive FC 300 Design Manual

FC 300 Design Guide
The load drives the motor (at constant output frequency from the frequency con-
1.
verter), ie. the load generates energy.
During deceleration ("ramp-down") if the moment of inertia is high, the friction is low
2.
and the ramp-down time is too short for the energy to be dissipated as a loss in the
frequency converter, the motor and the installation.
In-correct slip compensation setting may cause higher DC link voltage.
3.
The control unit may attempt to correct the ramp if possible (par. 2-17 Over-voltage Control.
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.
Mains Drop-out
During a mains drop-out, the frequency converter keeps running until the intermediate
circuit voltage drops below the minimum stop level, which is typically 15% below the
frequency converter's lowest rated supply voltage.
The mains voltage before the drop-out and the motor load determines how long it takes for the inverter to coast.
Static Overload in VVC
When the frequency converter is overloaded (the torque limit in par. 4-16/4-17 is reached),
the controls reduces the output frequency to reduce the load.
If the overload is excessive, a current may occur that makes the frequency con-
verter cut out after approx. 5-10 s.
Operation within the torque limit is limited in time (0-60 s) in par. 14-25.

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
chapter How to Programme.

Safe Stop Operation (FC 302 Only)

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The FC 302 can perform the Designated Safety Function "Uncontrolled Stopping by removal of power"
(as defined by draft IEC 61800-5-2) or Stop Category 0 (as defined in EN 60204-1).
It is designed and approved suitable for the requirements of Safety Category 3 in EN
954-1. This functionality is called Safe Stop.
Prior to integration and use of FC 302 Safe Stop in an installation, a thorough risk analysis
on the installation must be carried out in order to determine whether the FC 302 Safe Stop
functionality and safety category are appropriate and sufficient.
The Safe Stop function is activated by removing the voltage at Terminal 37 of the Safe Inverter. By connecting
the Safe Inverter to external safety devices providing a safe relay, an installation for a safe Stop Category 1
can be obtained. The Safe Stop function of FC 302 can be used for asynchronous and synchronous motors.
Safe Stop activation (i.e. removal of 24 V DC voltage supply to terminal 37)
does not provide electrical safety.
50
Introduction to FC 300
plus mode
MG.33.B4.02 - VLT is a registered Danfoss trademark