3 Functions
3.1 Safety Functions
International standards EN ISO 13850 and EN IEC 60204-1 specify the functional requirements and design principles of emergency stop
devices.
In control systems where there is a risk of equipment damage or personal injury, safety-related parts of control systems (SRP/CS) are
required to minimize the risk. SRP/CS include the following general components:
Detect
Process
Switch
Sensor
for exmple FC 302
e30be101.11
Illustration 5: Sensor-Logic-Actuator Safety Chain
Safety functions are defined based on both the application and the hazard. They are often specified in a Type C standard (a product
standard), which provides precise specifications for special machines. If a C standard is not available, the macine designer defines the
safety functions. Typical safety functions are described in more detail in EN ISO 13849-1, section 5, Specification of Safety Functions.
The safety functions for drive systems are described in IEC 61800-5-2.
N O T I C E
When designing the machine application, consider timing and distance for a coast to stop (Stop Category 0 or Safe Torque Off
(STO)). For more information regarding stop categories, refer to EN IEC 60204-1.
3.2 Safe Torque Off - STO
The safety function Safe Torque Off disconnects power to the motor. It is implemented via the shutdown path of the drive and the safe
outputs of the safety option.
Features of the safety subfunction
• The motor becomes torque-free and no longer generates any hazardous movements.
• The safety function STO corresponds to a Category 0 stop (uncontrolled stop) in accordance with EN IEC 60204-1.
• The safety subfunction Safe Torque Off corresponds to a category 0 stop (uncontrolled stop) in accordance with EN IEC 60204-1.
Functions
Installation Guide | VLT®Safety Option MCB 152
AN327351953089en-000101 / 130R0578
14 | Danfoss A/S © 2020.02
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