2 Engineering
2.1 Distinction from other regulations
26
CMD(24VDC), CMDTD
08/23 MN121001ZU-DE/EN
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2 Engineering
2.1 Distinction from other regulations
The safety-related part of the CMD contactor monitoring device‘s control
system has EN/ISO 13849-1 approval. The CMD is used for safety-related
applications in machine control systems. It has not been assigned to a
SIL category as per IEC/EN 61508. The system must be set up as per
IEC/EN 60204-1.
2.2 Performance Level
The CMD contactor monitoring device can be used to set up control systems
that meet the requirements of performance level (PL) “d” as per
EN/ISO 13849-1. The control system‘s setup meets the requirements of
category 3 as per EN/ISO 13849-1.
In order to reach a PL of “d“, a common-cause failure (CCF) analysis must be
performed for the control system.
The control system must meet the requirements of one of the following two
combinations of the average diagnostic coverage (DC
avg
) and the mean time
to dangerous failure (MTTF
D
):
•
DC
avg
= low and MTTF
D
= medium to high, or
•
DC
avg
= medium and MTTF
D
= medium.
2.3 Control system of category 3
The CMD contactor monitoring device can be used in combination with DOL
starters or reversing starters. The schematics are shown in
2.4 Average diagnostic coverage DC
avg
Disconnection in the event of a hazardous situation is implemented from
two units that are included in the calculation as parallel channels:
•
Channel 1: contactor,
•
Channel 2: series connection of the CMD and undervoltage release of
the motor-protective circuit-breaker/circuit-breaker.
The mirror contacts used allows a DC
avg
= 99 % to be applied to channel 1.
￫
Two CMD relays are required in reversing starter circuits.
To attain category 3, faults were excluded by wiring inside a
control cabinet.
On disconnection via the undervoltage release, a time delay of
100 ms ±20 % can occur.
An enable circuit must be protected with a max. 2 A gG/gL fuse
to protect the internal relay contacts.
Содержание CMD(24VDC)
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