Danfoss VLT AutomationDrive FC 302 Design Manual page 28

Product Features
When the load is held by the mechanical brake, its size cannot be determined, only its direction. The moment the
brake opens, the motor must take over the load. To facilitate the takeover, a user-defined torque
(parameter 2-26 Torque Ref) is applied in the hoisting direction. This process is used to initialize the speed controller
that finally takes over the load. To reduce wear on the gearbox due to backlash, the torque is ramped up.
3. Release the brake.
When the torque reaches the value set in parameter 2-26 Torque Ref, the brake is released. The value set in
parameter 2-25 Brake Release Time determines the delay before the load is released. To react as quickly as possible
on the load-step that follows after brake release, the speed-PID control can be boosted by increasing the propor-
tional gain.
5 5
Motor
Speed
Torque
Ref.
Brake
Relay
High
Low
Mech Brake
Feedback
High
Low
Open
Mech Brake
Position
Closed
Gain Boost or
Postion Control
Illustration 5.8 Brake Release Sequence for Hoist Mechanical Brake Control
Parameter 2-26 Torque Ref to parameter 2-33 Speed PID Start Lowpass Filter Time are only available for the hoist mechanical
brake control (flux with motor feedback). Parameter 2-30 Position P Start Proportional Gain to parameter 2-33 Speed PID Start
Lowpass Filter Time can be set up for smooth transition change from speed control to position control during
parameter 2-25 Brake Release Time - the time when the load is transferred from the mechanical brake to the drive.
Parameter 2-30 Position P Start Proportional Gain to parameter 2-33 Speed PID Start Lowpass Filter Time are activated when
parameter 2-28 Gain Boost Factor is set to 0. See Illustration 5.8 for more information.
NOTICE
For an example of advanced mechanical brake control for hoisting applications, see chapter 12 Application Examples.
26
Torque Ramp Brake Release
Up Time Time
p. 2-27 p. 2-25
Torque Ref. p. 2-26
W22
Active
Contact no.1
E.g. DI32 [70] Mech. Brake Feedback
Contact no.2
OPTIONAL
E.g. DI33 [71] Mech. Brake Feedback
Gain Boost. p. 2-28
Danfoss A/S © 01/2018 All rights reserved.
VLT® AutomationDrive FC 302
Ramp 1 Up
P. 3-41
A22
Active
Ramp 1 Down Stop Delay Activate Brake
P. 3-42 P. 2-24 Delay
P. 2-23
A22
Active
Torque Ramp
Down Time
p. 2-29
W22
Active
MG38C202