Functional safety
326
9.
FUNCTIONAL SAFETY
Cabling and grounding
322
DDS
HARDWARE
Ref.1310
9.8 Cabling and grounding
Safe Torque Off (STO)
The following recommendations must be taken into account when design-
ing the STO safety function:
A fuse MUST be installed that can limit the current of at least the STO
channel input of the AXD/SPD drive (pin 2 “Drive Enable” of X2).
FAGOR recommends installing a “1 A” slow fuse to limit the input cur-
rent through this pin. In the case of the figure where a safety relay has
been used, the fuse may be installed on the 24 V DC line to activate
both the AXD/SPD input and the external main contactor so it also
protects the internal contacts of the safety relay.
Try keeping power cables and signal cables apart from each other.
Run the STO channels activating cables through separate conduits
Install an intermediate auxiliary relay to activate the coil of the contac-
tor for high power units were the consumption current and peak cur-
rent of the external main contactor is significant; although the mirror
contact in series with the start button must belong to the external main
contactor. Never to the intermediate relay.
DDS system in general
The instructions regarding the cabling and grounding when installing Fa-
gor Automation's Digital Drive System are described in chapter
8. INSTA-
LLATION
in this manual.
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