Danfoss VLT AutomationDrive FC 300 Design Manual page 46

FC 300 Design Guide
1. Pre-magnetize the motor
In order to ensure that there is a hold on the motor and to verify that it is mounted correctly, the
motor is first pre-magnetized.
2. Apply torque against the closed brake
When the load is held by the mechanical brake, its size cannot be determined, only its direction.
The moment the brake opens, the load must be taken over by the motor. To facilitate the take-
over, a user defined torque, set in par. 2-26, is applied in hoisting direction. This will be used to
initialize the speed controller that will finally take over the load. In order to reduce wear on the
gearbox due to backlash, the torque is ramped up.
3. Release brake
When the torque reaches the value set in par. 2-26 Torque Ref, the brake is released. The value
set in par. 2-25 Brake Release Time determines the delay before the load is released. In order
to react as quickly as possible on the load-step that follows upon brake release, the speed-PID
control can be boosted by increasing the proportional gain.
Brake release sequence for hoist mechanical brake control
Cabling
EMC (twisted cables/shielding)
To reduce the electrical noise from the wires between the brake resistor and the frequency converter,
the wires must be twisted.
For enhanced EMC performance a metal screen can be used.
Smart Logic Control
The Smart Logic Control (SLC) is essentially a sequence of user defined actions (see par. 13-52) executed
by the SLC when the associated user defined event (see par. 13-51) is evaluated as TRUE by the SLC.
Events and actions are each numbered and are linked in pairs called states. This means that when event
[1] is fulfilled (attains the value TRUE), action [1] is executed. After this, the conditions of event [2] will
be evaluated and if evaluated TRUE, action [2]will be executed and so on. Events and actions are placed
in array parameters.
Only one event will be evaluated at any time. If an event is evaluated as FALSE, nothing happens (in the
SLC) during the present scan interval and no other events will be evaluated. This means that when the
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Introduction to FC 300
MG.33.B8.02 - VLT ® is a registered Danfoss trademark