Sbc Before Sto - ABB FSO-21 User Manual

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SBC before STO

The operation of the SBC before the STO function (negative SBC delay) is described
in the time diagrams and tables below. For configuration, see section
configure SBC before STO
The reason to use a negative SBC delay is to have the mechanical brake closed just
before the drive STO circuit is opened.
Without an encoder
Motor speed
A
C
1
2
A SBC delay (parameter SBC.12): Time from the activation of the drive STO to the moment
when the FSO activates the SBC function (brake)
the FSO activates the SBC before the drive STO. If the value is zero, the FSO activates
the SBC and drive STO functions at the same time.
B SBC time to zero speed (parameter SBC.13): Time from the SBC activation to the
moment when the safety function is completed and the STO completed indication
(parameter STO.22) goes on. The acknowledgment becomes allowed. You must set this
to the estimated time in which the motor brakes to a stop from the maximum speed.
C Response time (depends on system configuration, see page 437)
on page 268.
SBC.12
B
3
SBC.13
4
.
In this case the value is negative and
Safety functions 63
How to
Time
5 6
STO request
Drive STO state
& indication
SBC output
STO completed
indication