Danfoss VLT AutomationDrive FC 302 - Page 27

Start
term.18
1=on
0=o
Shaft speed
Start delay time
on
o
Brake delay time
Time
Output current
Relay 01
Pre-magnetizing
current or
DC hold current
Reaction time EMK brake
Par 2-20
Release brake current
Par 1-76 Start current/
Par 2-00 DC hold current
Par 1-74
Start speed
Par 2-21
Activate brake
speed
Mechanical brake
locked
Mechanical brake
free
Par 1-71
Par 2-23
130BA074.12
Illustration 5.7 Mechanical Brake Control in Open Loop
5.4.2 Mechanical Brake Using Closed-loop Control
The VLT
®
AutomationDrive FC 302 features a mechanical brake control designed for hoisting applications and supports the
following functions:
•
2 channels for mechanical brake feedback, oering protection against unintended behavior resulting from a broken
cable.
•
Monitoring the mechanical brake feedback throughout the complete cycle. Monitoring helps protect the
mechanical brake - especially if more drives are connected to the same shaft.
•
No ramp up until feedback conrms that the mechanical brake is open.
•
Improved load control at stop.
•
The transition when motor takes over the load from the brake can be congured.
Parameter 1-72 Start Function [6] Hoist Mech. Brake Rel activates the hoist mechanical brake. The main dierence compared to
the regular mechanical brake control is that the hoist mechanical brake function has direct control over the brake relay.
Instead of setting a current to release the brake, the torque applied against the closed brake before release is dened.
Because the torque is dened directly, the set-up is more straightforward for hoisting applications.
The hoist mechanical brake strategy is based on the following 3-step sequence, where motor control and brake release are
synchronized to obtain the smoothest possible brake release.
1. Pre-magnetize the motor.
To ensure that there is a hold on the motor and to verify that it is mounted correctly, the motor is
rst pre-
magnetized.
2. Apply torque against the closed brake.
Product Features Design Guide
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