The 3RB1257-0KB20: Rated for continuous or individual mounting, the relay connects to the main circuit via busbar and to the auxiliary circuit via screw terminals. The DC 24 V control supply and monostable ground-fault signaling outputs integrate into standard 24 VDC control panels.
Siemens 3RB1257-0KB20 Overload Relay, 125-500A, Discontinued
MPN3RB1257-0KB20
Siemens 3RB1257-0KB20, discontinued overload relay, 125-500 A, size S10/S12, Class 5-30, busbar main circuit, screw terminal aux, ground fault detection, DC 24 V.
Sourced new & surplus through independent channelsAuthenticity-screened · ESD-safe packingListing updated Jul 2026
Product details
Frequently asked questions
What is 3RB1257-0KB20 used for?
It is an overload relay for full motor protection, rated 125-500 A, size S10/S12, with Class 5-30 trip curve, busbar main circuit connection, and integrated ground fault detection with monostable signaling at DC 24 V.
Where can I buy 3RB1257-0KB20?
Sourced and quoted to order against an RFQ through independent distribution; availability and current pricing are confirmed at quote time.
MPN
3RB1257-0KB20