Safe Torque Off
6-27
890CS Common Bus Supply - Frames B & D; 890CD Common Bus Drive and 890SD Standalone Drive - Frames E & F
STO Implementation with Safety Control Unit
This example improves on the previous one by showing the resetting from a STO stop. The example shows
wiring and terminal numbering for a Siemens 3TK2827, but similar products are available from other vendors.
The use of this Siemens part does not imply it is suitable for the user’s application. The user must select and
assess appropriate equipment.
Note 1: Refer to manufacturers instructions for wiring and earthing detail.
Note: On power-up, the safety control unit outputs are OPEN; thus the STO state is requested of the 890. The
latter responds by energising KA1 if both channels are active and healthy. KA1 is used as a self-check for the
reset cycle of the safety control unit. If a reset cannot be achieved due to KA1 being de-energised, a fault may be
present and must be resolved by the user before relying on the STO function. See Fault Operation on page 6-16.
STO
DRIVE
START
DRIVE
STOP
SAFETY
DEMAND
24
VDC
SAFETY CONTROL UNIT
A
1
Y
12
Y
11
Y
10
RESET
K
A
1
K
A
1
A
2
POWER
SUPPLY
*
Note
1
THIS WIRING MUST BE WITHIN THE CONTROL CUBICLE
.
PE
Y
33
Y
34
14
24
Y
21
Y
22
13
23
X
11
/
01
X
11
/
03
X
11
/
06
X
15
/
02
X
15
/
03
X
14
/
03
X
11
/
04
X
11
/
05
X
11
/
02
X
14
/
04
0
V