For an introduction to the 3RU and 3RB overload relays, together with the general data on the various series and the assignments of the overload relays to the contactors, see the following PDF.
Connection methods
3RU2 thermal overload relays
Sizes S00 and S0:
Main and auxiliary circuit: optionally screw or spring-type terminals
Sizes S2 and S3:
Main circuit: Screw terminals with box terminal
Auxiliary circuit: optionally screw terminals or spring-type terminals
3RB3 electronic overload relays
Sizes S00 and S0:
Main and auxiliary circuit: optionally screw terminals or spring-type terminals
Sizes S2 and S3:
Main circuit: Screw terminals with box terminal or as straight-through transformer
Auxiliary circuit: optionally screw terminals or spring-type terminals
3RB2 electronic overload relays
3RB20 and 3RB21 overload relays:
Size S6:
Main circuit: with busbar connection or as straight-through transformer
Auxiliary circuit: optionally screw terminals or spring-type terminals
Sizes S10/S12:
Main circuit: With busbar connection
Auxiliary circuit: optionally screw terminals or spring-type terminals
3RB22 to 3RB24 evaluation modules:
Screw or spring-type terminals
3RB29 current measuring modules:
Up to size S3: Straight-through transformers
From size S6:
Main circuit: With busbar connection
Auxiliary circuit: optionally screw terminals or spring-type terminals
