Hoist Mechanical Brake - Danfoss FC 300 Design Manual

FC 300 Design Guide
In hoisting/lowering applications, it must be possible to control an electro-mehanical brake.
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 frequency converter is unable to drive the motor, for example due to the load being too
heavy or due to the fact that the motor has not been mounted yet.
• Select Mechanical brake control
• The brake is released when the motor current exceeds the preset value in par. 2-20
• The brake is engaged when the output frequency is less than the frequency set in par. 2-21
Brake Speed [Hz]
and only if the frequency converter carries out a stop command.
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. 4-16
Mode are set lower than the current limit in par. 4-18
Limit
to "0", par. 14-26

3.9.2 Hoist Mechanical Brake

The VLT AutomationDrive features a mechanical brake control specifically designed for hoisting applications. The hoist mechanical brake is activated by
choice [6] in par. 1-72 Start Function
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.
Gain Boost Factor
By using par. 2-28
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. 2-26
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 ramped up.
3. Release brake
When the torque reaches the value set in par. 2-26
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.
[32] in par. 5-4* (or in par. 5-3*) before connecting the mechanical brake.
Current Limit
Trip Delay at Inverter Fault
to "0" and par. 14-10
. The main difference comed to the regular mechanical brake control, where a relay function monitoring the output
a quicker control when releasing the brake can be obtained. The hoist mechanical brake strategy is based on a 3-
Torque Ref the brake is released. The value set in par. 2-25
MG.33.BC.02 - VLT ® is a registered Danfoss trademark
3 Introduction to AutomationDrive FC 300
Release Brake Current .
Activate Brake Speed [RPM]
Torque Limit Motor Mode and par. 4-17
. Also it is recommendable to set par. 14-25
Mains Failure Coasting
to "[3],
Torque Ref
, is applied in hoisting direction. This
Brake Release Time
3
Activate
or par. 2-22
Torque Limit Generator
Trip Delay at Torque
".
determines
47