Function modules
8.3 Extended Brake Control
Drive functions
476 Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Examples
Starting against a closed brake
When the device is switched on, the setpoint is enabled immediately (if the required enable
signals are issued), even if the brake has not yet been released (p1152 = 1). The factory
setting p1152 = r0899.15 must be separated here. The drive starts to generate torque
against the closed brake. The brake is not opened until the motor torque or current (p1220)
has exceeded braking threshold 1 (p1221). Depending on the type and design of the brake,
the time required to completely open the brake differs. Note that once the braking threshold
torque has been exceeded, the operation enabling signal (r0899.2) is interrupted while the
brake is being opened (p1216) to ensure that the motor current does not exceed the
permissible limit values during this period and/or the motor torque generated does not
damage the brake. Interval p1216 must be set on the basis of the time the brake actually
requires to release.
In the case of emergency braking, electrical and mechanical braking should be realized at
precisely the same time. This can be achieved by using OFF3 as a tripping signal for
emergency braking:
p1219[0] = r0898.2 and p1275.00 = 1 (OFF3 to "Close brake immediately" and invert signal).
To ensure that the frequency converter does not operate against the brake, the OFF3 ramp
(p1135) should be set to 0 seconds. Regenerative energy can be generated, which must be
either fed back to the line supply or dissipated by means of a braking resistor.
Service brake on crane drives
For cranes with manual control, it is important that the drive responds immediately when the
control lever is moved (master switch). The drive is switched on with an ON command
(p0840) (the pulses are enabled). Speed setpoint (p1142) and speed controller (p0856) are
inhibited. The motor is magnetized. The magnetization time required for three-phase motors
(1-2 s), therefore, no longer applies.
Now, only the brake opening time will delay the motor starting to rotate following activation of
the master switch. If the master switch is moved (deflected), then there is a "setpoint enable
from the control" (bit interconnected with p1142, r1229.3, p1224.0). The speed controller is
enabled immediately. Once the brake opening time has elapsed (p1216), the speed setpoint
is enabled. When the master switch is in the zero position, the speed setpoint is inhibited
and the drive brakes along the deceleration ramp of the ramp-function generator. The brake
closes when the speed drops below the standstill limit (p1226). After the brake closing time
(p1217), the speed controller is inhibited (no motor force!). The extended brake control is
used.
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