Safe Torque Off 6-15
AC30 series Variable Speed Inverter
PULSED INPUTS
Some safety equipment, e.g. safety PLCs, regularly pulse the two STO inputs independently in order to detect a short circuit between them. This is
commonly known as OSSD (Output Signal Switch Device). The inverter STO inputs are immune to such pulses when they are less than 2ms in width.
The product will not react to such pulses and therefore will not inadvertently invoke the STO function.
States:
1 Both inputs are low. Drive is tripped and STO prevents the drive from starting. User output is ON. This is the “safe torque off” state of
the drive.
2 Both inputs are high, but regularly pulse low independently. External equipment can thus detect a short circuit between the two STO
user inputs. Each input must remain low for 6ms (typical) before the inverter reacts to it.
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