NORD Drivesystems BU0230 - Manual (Page 37)

2 Description of function
BU 0230 GB-2712 37
2.4.3 Simple restart block
Safety Category 4 as per DIN ISO 13849-1 can be achieved with a direct dual-channel triggering of the "safe
pulse block" with the aid of a safe switching element. The following illustration shows an example with an
emergency stop switch (guided contacts, Safety Category 4).
GND SH
24V SH
Frequency inverter
89
Emergency stop button
24V
Shielded cable to eliminate
errors as per
DIN EN ISO 13849-2
88
To achieve safety category 4, fault exclusion as per EN 13849-2 Sec. D.5 must be possible for the upstream
components (hard-wiring and dual-channel buttons with independent, positive-opening contacts). I.e., in this
example, the emergency-stop button and the wiring must be designed in such a way that short-circuiting at the
emergency-stop button and to other live systems can be ruled out.
NOTE
After triggering the "safe pulse block“, the inverter shows the acknowledgeable fault E018
(18.0 Safety circuit).
NOTE
In this example, there is no reset circuit as is the case with the protective switching devices. If
the result of risk analysis is that cancellation of the stop command must be acknowledged by
intended manual action then the resetting requirements can be fulfilled organisationally (e.g. by
an emergency-stop button with key releasing device and storage of the key away from the
machine).
NOTE
It is recommended that the „automatic fault clearance“ (P506) and „automatic start-up“ (P428)
functions are not used in combination with each other (see BU 0200 GB), as the drive would
otherwise start up immediately after unlocking the emergency-off button.