Danfoss VLT AutomationDrive FC 302 Design Manual page 27

Product Features
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 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, offering 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 confirms that the mechanical brake is open.
•
Improved load control at stop.
•
The transition when motor takes over the load from the brake can be configured.
Parameter 1-72 Start Function [6] Hoist Mech. Brake Rel activates the hoist mechanical brake. The main difference 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 defined.
Because the torque is defined 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 first pre-
magnetized.
2. Apply torque against the closed brake.
MG38C202
Design Guide
Par 1-74
Start speed
Par 1-76 Start current/
Par 2-00 DC hold current
Reaction time EMK brake
Danfoss A/S © 01/2018 All rights reserved.
Par 2-20
Release brake current
Par 2-21
Activate brake
speed
5
Time
25
5