Program features 107
Mechanical brake control
A mechanical brake can be used for holding the motor and driven machinery at zero
speed when the drive is stopped, or not powered. The brake control logic observes
the settings of parameter group 44 Mechanical brake control as well as several
external signals, and moves between the states presented in the diagram on page
108. The tables below the state diagram detail the states and transitions. The timing
diagram on page 110 shows an example of a close-open-close sequence.
The mechanical brake control logic operates on a 10 ms time level.
Inputs of the brake control logic
The start command of the drive (bit 5 of 06.16 Drive status word 1) is the main control
source of the brake control logic. An optional external open/close signal can be
selected by 44.12 Brake close request. The two signals interact as follows:
• Start command = 1 AND signal selected by 44.12 Brake close request = 0
→
Request brake to open
• Start command = 0 OR signal selected by 44.12 Brake close request = 1
→
Request brake to close
Another external signal – for example, from a higher-level control system – can be
connected via parameter 44.11 Keep brake closed to prevent the brake from opening.
Other signals that affect the state of the control logic are
• brake status acknowledgment (optional, defined by 44.07 Brake acknowledge
selection),
•bit 2 of 06.11 Main status word (indicates whether the drive is ready to follow the
given reference or not),
•bit 6 of 06.16 Drive status word 1 (indicates whether the drive is modulating or
not),
• optional FSO-xx safety functions module.
Outputs of the brake control logic
The mechanical brake is to be controlled by bit 0 of parameter 44.01 Brake control
status. This bit should be selected as the source of a relay output (or a digital
input/output in output mode) which is then wired to the brake actuator through a relay.
See the wiring example on page 111.
The brake control logic, in various states, will request the drive control logic to hold
the motor, increase the torque, or ramp down the speed. These requests are visible in
parameter 44.01 Brake control status.
Settings
Parameter group 44 Mechanical brake control (page 357).
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