Danfoss VLT AutomationDrive EZ FC 321 Operating Manual page 18

Safe Torque Off
Operating Guide
When using internal 24 V DC supply (terminal 12), the number of parallel inputs (terminal 37) is limited to 3, otherwise the availa-
ble output power is exceeded.
Design features
• The circuit can be used up to Category 3, PL d, or SIL2.
• For PL d, the complete safety functions have to be calculated (MTTFd).
• Use basic safety principles.
• Device used for activation of STO and safety relay must be suitable for the selected category, PL or SIL.
When implementing the emergency stop, pay attention to the following tips:
• Any non-safety related standards should be fulfilled for the application and its components.
• The application designer is responsible for selecting suitable components.
• The cable shown in bold in
• To fulfill PL d, the MTTFd and DC for the entire safety function has to be calculated.
Implementation in SISTEMA using Danfoss VLT library
As an example, use the subsystem "VLT® AutomationDrive EZ FC 321 Safe Torque Off (Terminal 37)". It is not necessary to edit all the
parameters which are set in the library. Put the subsystem into the safety function as often as the number of drives that are present
on the single STO line.
SB emergency
stop device
Illustration 9: Safety-related Block Diagram
18 | Danfoss A/S © 2022.11
N O T I C E
Illustration 8 has to be short-circuit protected according to ISO 13849-2, table D.4.
SB FC300 safe stop
(terminal 37)
SB safety relay
from Danfoss VLT library
Application Examples
SB FC300 safe stop SB FC300 safe stop
(terminal 37)
from Danfoss VLT library from Danfoss VLT library
AQ355238304444en-US0301 / 130R0955
(terminal 37)