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Siemens Industry Online Support
Siemens AG
Entry type: FAQ, Entry ID: 109481229, Entry date: 07/27/2016
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Confirmation regarding connection of 3RT2 contactors and contactor assemblies to 3RK3 MSS, 3SK1 and 3SK2 safety relays.

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This entry includes confirmation with regard to the question of whether 3RT2 contactors and contactor assemblies can be connected to 3RK3 MSS, 3SK1 and 3SK2 safety relays.

QUESTION:

Can all 3RT2 contactors and contactor assemblies be connected to 3RK3 MSS, 3SK1 and 3SK2 safety relays without any issue?

 


ANSWER:

All 3RT2 contactors and contactor assemblies can be connected to 3RK3 MSS, 3SK1 and 3SK2 safety relays.
When connecting a 3RT203.-. NB3.-.... and 3RT203.-.KB4.-.... to a 3SK1 Advanced 3SK1122-.CB4. relay with adjustable OFF-delay time, an additional 1.2 kΩ resistor must be connected in parallel to A1-A2 on the 3RT20.

Reason:
A capacitor is built into the contactor coils of 3RT203.-. NB3.-.... and 3RT203.-.KB4.-.... units.
The capacitor shapes the pulses to the contactor coil and hampers the dark test for electronic enabling circuits.
For this reason, an external resistor is necessary in some cases.
For more details, please see the attached confirmation (634.1 KB).


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