Hoist Mechanical Brake - GE AF-650 GP Design Manual

NB!
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 t such as a contactor, etc.
If the frequency converter is in alarm mode or in an over voltage situation, the mechanical brake cuts in.
NB!
For hoisting applications make sure that the torque limits in par. F-40 Torque Limiter (Driving) and par. F-41 Torque Limiter (Braking) are set lower than the current
3
limit in par. F-43 Current Limit. Also it is recommendable to set par. SP-25 Trip Delay at Torque Limit to "0", par. SP-26 Trip Delay at Drive Fault to "0" and
par. SP-10 Line failure to "[3], Coasting".

3.9.2 Hoist Mechanical Brake

The AF-650 GP features a mechanical brake control specifically designed for hoisting applications. The hoist mechanical brake is activated by choice [6] in
par. F-25 Start Function. The main difference comed 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 par. 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 par. B-26 Torque Ref, is applied in hoisting direction. This 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 acceled.
3. Release brake
When the torque reaches the value set in par. B-26 Torque Ref the brake is released. The value set in par. 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.
Illustration 3.4: 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 par. B-24 Stop Delay, the frequency converter starts without
applying the mechanical brake (e.g. reversing).
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AF-650 GP Design Guide