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In hoisting/lowering applications, it must be possible to control an electro-mechanical 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 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 par. 5-4* (or in par. 5-3*) before connecting the mechanical brake.
•
The brake is released when the motor current exceeds the preset value in par. 2-20
Release Brake Current
.
•
The brake is engaged when the output frequency is less than the frequency set in par. 2-21
Activate Brake Speed [RPM]
or par. 2-22
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 par. 4-16
Torque Limit Motor Mode
and par. 4-17
Torque Limit Generator
Mode
are set lower than the current limit in par. 4-18
Current Limit
. Also it is recommendable to set par. 14-25
Trip Delay at Torque
Limit
to “0”, par. 14-26
Trip Delay at Inverter Fault
to “0” and par. 14-10
Line Failure
to “[3],
Coasting
”.
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
. 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 set-up is more
straightforward for hoisting applications.
By using par. 2-28
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 Introduction to AutomationDrive FC 300
FC 300 Design Guide
3-32
MG.33.BC.22 - VLT
®
is a registered Danfoss trademark
3