Appendix: Safe torque off (STO) 403 24 V auxiliary voltage load (I/O, panel load, used fieldbus or STO circuits; max. 200 mA) of the drive supplying the STO circuit (see section Control connection data on page 369). When using external supply, all analog grounds (AGND) of the drives must be chained together. Note: Daisy chaining lowers the total system safety integrity level, which needs to be calculated case by case for each system.
Start-up and commissioning Always test the operation and reaction of the STO function before commissioning.
Technical data STO components STO safety relay type General requirements Output requirements No. of current paths Switching voltage capability Switching current capability Maximum switching delay between contacts Example 1 Type and manufacturer Approvals
IEC 61508 and/or EN/ISO 13849-1 2 independent paths (one for each STO path) 30 V DC per contact 100 mA per contact 200 ms Simple SIL3 approved safety relay PSR-SCP- 24UC/ESP4/2X1/1X2 by Phoenix Contacts EN 954-1, cat 4; IEC 61508, SIL3
Example 2 Type and manufacturer
Programmable safety logic PNOZ Multi M1p by Pilz
Approvals
EN 954-1, cat 4; IEC 61508, SIL3; and ISO 13849-1, PL e
STO connection Input for external STO supply
24 V DC ± 10%, load 25 mA
Input impedance
Rin = 2 kohm
Load Output
12 mA / channel Maximum load 200 mA depending on I/O load
STO cable Type Conductor size Maximum length Tightening torque
2×2 cables, low voltage, single shielded, twisted pair cable 1.5…0.25 mm2 (16…24 AWG) Max. 25 m between STO inputs and the operating contact 0.5 N·m (4.4 lbf·in)