GE AF-650 GP Design And Installation Manual page 76

Application Set-Up Examples
defined. Because the torque is defined directly the set-up
is more straightforward for hoisting applications.
By using parameter B-28 Gain Boost Factor a quicker control
when releasing the brake can be obtained. The hoist
mechanical brake strategy is based on a 3-step sequence,
where motor control and brake release are synchronized in
order to obtain the smoothest possible brake release.
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.
Illustration 6.24 Brake release sequence for hoist mechanical brake control
I) Activate brake delay: The frequency converter starts again from the mechanical brake engaged position.
II) Stop delay: When the time between successive starts is shorter than the setting in parameter B-24 Stop Delay, the frequency
converter starts without applying the mechanical brake (that is reversing).
NOTICE
For an example of advanced mechanical brake control
for hoisting applications, see chapter 6.2 Application
Examples.
MG35M402
AF-650 GP™ Design and Installation Guide
3.
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The moment the brake opens, the load must be
taken over by the motor. To facilitate the
takeover, a user-defined torque, set in
parameter B-26 Torque Ref, is applied in hoisting
direction. This is used to restore the speed
controller that will finally take over the load. In
order to reduce wear on the gearbox due to
backlash, the torque is acceled.
Release brake
When the torque reaches the value set in
parameter B-26 Torque Ref the brake is released.
The value set in parameter B-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 after brake release, the
speed-PID control can be boosted by increasing
the proportional gain.
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