Danfoss FC 300 Design Manual page 49

FC 300 Design Guide
3-step sequence
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 takeover, a user defined torque, set in par. 2-26
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
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.
Figure 3.6: Brake release sequence for hoist mechanical brake control
I) Activate brake delay: The adjustable frequency drive starts again from the
II) Stop delay : When the time between successive starts is shorter than the setting in par. 2-24
starts without applying the mechanical brake (e.g., reversing).
NOTE!
For an example of advanced mechanical brake control for hoisting applications, see section
3.9.3 Brake Resistor Cabling
EMC (twisted cables/shielding)
To reduce the electrical noise from the wires between the brake resistor and the adjustable frequency drive, the wires must be twisted.
For enhanced EMC performance, a metal shield can be used.
Torque Ref , the brake is released. The value set in par. 2-25
mechanical brake engaged
MG.33.BC.22 - VLT ® is a registered Danfoss trademark
3 Introduction to AutomationDrive FC 300
Torque Ref
, is applied in hoisting direction. This
Brake Release Time
position.
Stop Delay , the adjustable frequency drive
Application Examples
3
determines
3-33