ABB ACS880 Series, Firmware Manual

Page: 113 / 764

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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 Brake
state diagram on page
114 . The tables below the state diagram detail the states
and transitions. The timing diagram on page 116 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 6.16 ) is the main control source of the
brake control logic. An optional external open/close signal can be selected by
44.12 . The two signals interact as follows:
• Start command = 1 AND signal selected by parameter 44.12 = 0 → Request
brake to open
• Start command = 0 OR signal selected by parameter 44.12 = 1 → Request brake
to close
Another external signal – for example, from a higher-level control system – can be
connected via parameter
44.11 to prevent the brake from opening.
Other signals that affect the state of the control logic are
• brake status acknowledgement (optional, defined by 44.7 ),
• bit 2 of 6.11 (indicates whether the drive is ready to follow the given reference
or not),
• bit 6 of 6.16 (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 44.1 . 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
117 .
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
44.1 .
Program features 113