6-3 Safe Torque Off 
AC30V series Variable Speed Drive 
Alignment to European Standards 
EN ISO13849-1:2008 
(Safety of machinery – Safety-related parts of control systems) 
 
STO aligns internally to the following aspects of this standard: 
•  Architecture according to Category 3: 
 
Solid lines represent the STO control paths. 
Dashed lines represent reasonably practicable fault detection. 
Key:   I1, I2 = user terminal 
  L1, L2 = logic 
  O1, O2 = methods of enabling or disabling output power devices 
  i
mxy
 = interconnecting means 
  m
x
 = monitoring 
  c = cross monitoring 
•  Category 3 general requirements are: 
A single failure, and any consequential failures, will not lead to loss of the STO safety function. 
Failure of more than one component can lead to the loss of the STO safety function. 
I1 
L1  O1 
I2 
L2  O2 
m1a 
m2a 
m1b 
m2b 
1 
2