Aerotech Automation1 iXC2, Hardware Manual

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2.4.4. STO Diagnostics
Activation of STO means removing power from the drive’s STO inputs. This is typically done by
pressing the emergency stop switch. The drive initiates a diagnostic check every time the STO is
activated after the Diagnostic Test Delay Time has elapsed. The diagnostic check verifies that each
channel has entered the safe state. The drive is held in the safe state if it determines that one of the
channels has not properly entered the safe state. An open circuit or short to 24 V in either
STO channel will result in this condition (refer to
Section 2.4.3. ). The Status Utility screen can be used
to verify the levels of the STO input signals while trouble shooting.
In order to meet the listed SIL level, the STO circuit must be activated (power removed from both
inputs) according to the interval specified in
Table 2-27 .
Table 2-30: STO Timing
Time Description Value
T1 STO Delay Time (STO input active to motor power off) 450-550 msec
T2
STO deactivated to motor power on (the software is typically
configured so that the motor does not automatically re-
energize).
< 1 msec
T3 Diagnostic Test Delay Time 550-610 msec
Figure 2-28: STO Timing
The software is typically configured to execute a controlled stop when the STO state is first detected.
If power is reapplied to the STO inputs before the STO Delay Time, an STO hardware shutdown will
not occur but a software stop may, depending on the width of the STO pulse. The controller will
ignore STO active pulses shorter in length than the STOPulseFilter parameter setting.
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