Danfoss VLT AutomationDrive FC 302 - Page 28

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-dened torque
(parameter 2-26 Torque Ref) is applied in the hoisting direction. This process is used to initialize the speed controller
that nally 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.
130BA642.12
A22
Active
W22
Active
W22
Active
A22
Active
High
Low
High
Low
Open
Closed
Motor
Speed
Torque
Ref.
Brake
Relay
Mech Brake
Feedback
Gain Boost or
Postion Control
Mech Brake
Position
Activate Brake
Delay
P. 2-23
Torque Ramp
Down Time
p. 2-29
Stop Delay
P. 2-24
Ramp 1 Down
P. 3-42
Ramp 1 Up
P. 3-41
Brake Release
Time
p. 2-25
Torque Ramp
Up Time
p. 2-27
Contact no.2
OPTIONAL
E.g. DI33 [71] Mech. Brake Feedback
Contact no.1
E.g. DI32 [70] Mech. Brake Feedback
Gain Boost. p. 2-28
Torque Ref. p. 2-26
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 (ux 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.
Product Features VLT® AutomationDrive FC 302
26 Danfoss A/S © 01/2018 All rights reserved. MG38C202
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