Using auxiliary contacts of 3RB / 3RU overload relays for switching large power contactors

This entry contains information for use of coupling relays together with 3RB / 3RU overload relays.

 

QUESTION:

Switching large power motors in hazardous areas: For controlling magnet coils of strong power contactors, can coupling relays be put in between the switching contacts of the 3RB / 3RU overload relay or does the 95/96 contact of the 3RB/ 3RU have to be switched directly into the control circuit of the contactor?

 

ANSWER:

As regards controlling power contactors with 3RB / 3RU overload relays, the following statement is valid: If the power consumption of the contactor coil to be controlled exceeds the ON and OFF switching capacity of the 3RB / 3RU overload relay, then an additional contactor or relay with sufficient switching capacity can be used as an interface for strengthening the contacts. This is also valid for applications for motor protection in hazardous areas.

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