Nord-drivesystems BU0530 User Manual download pdf (Page 26)

Functional safety with NORD SK 500E frequency inverters

26 BU 0530 GB-3712

2.3.3 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).

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

We recommend that the "automatic fault clearance“ (P506) and "automatic start-up" (P428)

functions are not used in combination with each other (See BU 0500 GB), as the drive would

otherwise immediately start up after unlocking the emergency-off button.

GND SH

24V SH

Frequency inverter

Emergency stop button

24V

Shielded cable to eliminate

errors as per

DIN EN ISO 13849-2

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Nord-drivesystems BU0530 User Manual Page 26