Danfoss VLT AutomationDrive FC 300 Design Manual page 51

Product Introduction
When [32] mechanical brake control is selected, the mechanical brake relay remains closed during start until the output
current is above the level selected in 2-20 Release Brake Current. During stop, the mechanical brake will close when the
speed is below the level selected in 2-21 Activate Brake Speed [RPM]. If the frequency converter is brought into an alarm
condition, such as an over-voltage situation, the mechanical brake immediately cuts in. This is also the case during Safe
Torque Off.
Start
1=on
term.18
0=o
Par 1-71
Start delay time
Shaft speed
Output current
Pre-magnetizing
current or
DC hold current
Par 2-23
Brake delay time
on
Relay 01
o
Mechanical brake
locked
Mechanical brake
free
Illustration 3.33 Mechanical Brake Control in Open Loop
To control the electro-magnetic brake, use the following steps:
1. Use any relay output or digital output (terminal 27 or 29). If necessary, use a contactor.
2. Ensure that the output is switched off as long as the frequency converter is unable to drive the motor. Examples
include the load being too heavy or the motor not being mounted.
3. Before connecting the mechanical brake, select [32] Mechanical brake control in parameter group 5-4* Relays (or in
group 5-3* Digital Outputs).
4. The brake is released when the motor current exceeds the preset value in 2-20 Release Brake Current.
5. The brake is engaged when the output frequency is less than the frequency set in 2-21 Activate Brake Speed [RPM]
or 2-22 Activate Brake Speed [Hz] and only if the frequency converter carries out a stop command.
NOTICE
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. If the frequency converter is in alarm mode or in an over voltage situation, the
mechanical brake cuts in.
For hoisting applications, make sure that the torque limits in 4-16 Torque Limit Motor Mode and 4-17 Torque Limit Generator
Mode are set lower than the current limit in 4-18 Current Limit. It is also recommended to set 14-25 Trip Delay at Torque Limit
to "0", 14-26 Trip Delay at Inverter Fault to "0" and 14-10 Mains Failure to [3] Coasting.
®
VLT AutomationDrive FC 300 Design Guide 90-1200 kW
Par 1-74
Start speed
Par 1-76 Start current/
Par 2-00 DC hold current
Reaction time EMK brake
MG34S202 - Rev. 2013-08-19
Par 2-20
Release brake current
3
Par 2-21
Activate brake
speed
Time
49
3