2 Description of the safety function STO
24 Festo – GDCP-CMMS-AS-G2-S1-EN – 1306NH – English
2.4.3 Restart after SS1 and STO
Before switching it on again, make sure that all hazards have been eliminated and the system can be
safely placed in operation again. A manual acknowledgment must be made through the optional S2
pushbutton if the risk evaluat ion of the application requires it (see switching example).
The timing diagram in S ec tion 2.4.4 has been c reated using the example of the speed adjustment under
consideration of the controller enable via DIN 5 at [X1]. For fieldbus applications, the controller enable
is additionally controlled via the respective fieldbus. Depending on the application, the operat ing mode
can also be parameterised using the parameterisation software.
To end the safety function SS 1 and switch the output stage of the motor controller active again, the
following steps must be taken ( timing diagram Section 2.4.4):
1. First, the control of the relay for switching the supply voltage of the output stage driver (2nd switch-
off path) must be switched through 24 V at Rel [ X3.2] (related to 0 V [X3.3]).
This switches on the internal driver supply.
2. The driver supply is recharged after no more than 20 ms (t8).
3. The potential-free acknowledgment c ontact NC1/NC2 [X3.5/6] is opened no later than 30 ms (t6)
after Rel [X3.2] is switched.
4. The switching time for the output stage enable DIN4 [X1.21] is freely selectable ( t9). The release
should take place simultaneously with activation of the 2nd switch-off path via Rel [X3.2], but must
be present at least 2.5 ms (t10) after the rising edge of the controller enable DIN5 [X1.9].
5. With the rising edge of the controller enable, after a time delay ≤ 5 ms ( t11), release of the motor
holding brake is triggered (if present) and the internal output stage enable takes place. For control
via the fieldbus, controller enable via fieldbus is also required befo rehand.
With FCT, a switch-on delay c an be set for the brake (t13). During this time, the drive is regulated to
speed “0”. After that, it is regulated to the set speed.
The time t13 is chosen so large that the brake c an open mechanically within t13.
6. No later than 720 ms (t7) after ending of the 2-channel request, the “H” on the 7-segments display
goes out.
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