
6-6
Safe Torque Off
890CS Common Bus Supply - Frames B & D; 890CD Common Bus Drive and 890SD Standalone Drive - Frames E & F
EN61800-5-2:2007 and EN61508
(Adjustable speed electrical power drive systems) and
(Functional safety of electrical/electronic/programmable electronic safety-related systems)
STO aligns to the following aspects of this standard:
•
Safety Integrity Level 3
Probability of dangerous random hardware failures per hour (PFH) must be
≤ 10
-7
Subsystems type A according to EN61508-2:2001 para 7.4.3.1.2
Hardware Fault Tolerance (HFT) = 1
Safe Failure Fraction (SFF) must be
≥ 90%