GE AF-650 GP Series, Design And Installation Manual

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Step-by-step Description
•
To control the mechanical brake, any relay output
or digital output (terminal 27 or 29) can be used.
If necessary, use a suitable contactor.
•
Ensure that the output is switched off as long as
the adjustable frequency drive is unable to drive
the motor, such as when the load is too heavy or
the motor has not been mounted, for example.
•
Select Mechanical brake control [32] in parameter
groupE-2# before connecting the mechanical
brake.
•
The brake is released when the motor current
exceeds the preset value in
B-20 Release Brake
Current .
•
The brake is engaged when the output frequency
is less than the frequency set in
B-21 Activate
Brake Speed [RPM] or B-22 Activate Brake Speed
[Hz] and only if the adjustable frequency drive
carries out a stop command.
NOTE!
For vertical lifting or hoisting applications it is strongly
recommended to ensure that the load can be stopped in
case of an emergency or a malfunction of a single part
such as a contactor, etc.
If the adjustable frequency drive is in alarm mode or in an
overvoltage situation, the mechanical brake cuts in.
NOTE!
For hoisting applications make sure that the torque limits
in
F-40 Torque Limiter (Driving) and F-41 Torque Limiter
(Braking) are set lower than the current limit in
F-43 Current Limit . Also it is recommendable to set
SP-25 Trip Delay at Torque Limit to “0”, SP-26 Trip Delay at
Drive Fault to “0” and SP-10 Line failure to “[3], Coasting ”.
6.6.4 Hoist Mechanical Brake
The AF-650 GP features a mechanical brake control specif-
ically designed for hoisting applications. The hoist
mechanical brake is activated by choice [6] in
F-25 Start
Function . The main difference compared to the regular
mechanical brake control, where a relay function
monitoring the output current is used, is that the hoist
mechanical brake function has direct control over the
brake relay. This means that instead of setting a current for
release of the brake, the torque applied against the closed
brake before release is defined. Because the torque is
defined directly, the setup is more straightforward for
hoisting applications.
By using
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.
The moment the brake opens, the load must be
taken over by the motor. To facilitate the
takeover, a user defined torque, set in
B-26 Torque Ref , is applied in hoisting direction.
This will be 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.
3. Release brake
When the torque reaches the value set in
B-26 Torque Ref , the brake is released. The value
set in 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 upon brake release, the speed-PID control
can be boosted by increasing the proportional
gain.
Application Setup Examples AF-650 GP
TM
Design and Installation Guide
DET-767A 6-25
6 6