ABB FSO-21, User Manual

Page: 74 / 540

74 Safety functions

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
How to
configure SBC before STO on page 335 .
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
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)
.
In this case the value is negative and
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 532 )
Drive STO state
& indication
STO request
Motor speed
Time
A
STO completed
indication
1
6 5
SBC output
3
B
4
SBC.12
SBC.13
C
2