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Siemens 3RU7126-1KB0 — Overload Relays

Siemens 3RU7126-1KB0 SIRIUS Thermal Overload Relay, 12.5 A,

MPN3RU7126-1KB0

Siemens SIRIUS thermal overload relay, 3RU7126-1KB0, S0 size, 12.5 A rated operational current, Class 10 trip, screw-type terminals, IP20 front and terminal protection.

Source DocumentedChannel stated on listing & quote
Condition PhotosReal unit photos / video on request
WhatsApp AnswersFast human replies for machine-down parts
Worldwide DispatchDHL/FedEx — transit quoted per order
Independent China distributor & sourcing agent· Listing updated Sep 2026

Specifications

3RU7126-1KB0 — Identification
ParameterValue
Product brand nameSIRIUS
Product designationThermal overload relay
Frame size (overload relay)S0
Combinable contactor sizesS0
3RU7126-1KB0 — Protection & Trip
ParameterValue
Overload current setting range9 ... 12.5 A
Trip classCLASS 10
Overload release typethermal
3RU7126-1KB0 — Electrical (main circuit)
ParameterValue
Rated operational current12.5 A
Poles (main circuit)3
Rated operating frequency50 ... 60 Hz
Rated insulation voltage (AC, pollution degree 3)690 V
Rated surge withstand voltage6 kV
Main current circuitscrew-type terminals
Power loss at rated current (hot)6.6 W
Per pole2.2 W
3RU7126-1KB0 — Auxiliary contacts
ParameterValue
Switching current at 24 V3 A
Switching current at 230 V2 A
3RU7126-1KB0 — Connection & Mounting
ParameterValue
Mounting / fastening methodContactor mounting
Mounting positionwith vertical mounting surface +/-135° rotatable, with vertical mounting surface +/- 45° tiltable to the front and back
Main-circuit connector arrangementTop and bottom
Auxiliary/control circuit connection typescrew-type terminals
Conductor cross-section: solid or stranded2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)
Conductor cross-section: finely stranded with ferrule2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)
3RU7126-1KB0 — Environmental
ParameterValue
Operating temperature-20 ... +55 °C
Transport temperature-25 ... +70 °C
Relative humidity, operating0 ... 90 %
Max. installation altitude2 000 m
3RU7126-1KB0 — Mechanical
ParameterValue
Width45 mm
Height97 mm
Depth96 mm

Product details

The Siemens 3RU7126-1KB0 is a SIRIUS thermal overload relay, size S0, designed to protect three-phase AC motor circuits against overload and phase loss. It mounts directly onto a SIRIUS contactor (S0 frame) via the contactor mounting fastening method, forming a compact motor starter assembly for DIN-rail or panel integration. Rated operational current is 12.5 A at up to 690 V AC/DC, 50/60 Hz. Class 10 trip curve. The relay is rated for a -20 to +55 °C operating ambient, with storage down to -25 °C.

Mounts directly onto SIRIUS S0 contactors. Side spacing to grounded parts requires 6 mm minimum. Screw terminals for both main and auxiliary circuits: main terminals torque to 2–2.5 N·m, auxiliary to 0.8–1.2 N·m. Accepts 2× (0.5–1.5 mm²) solid/stranded or 2× (0.75–2.5 mm²) with ferrules. The relay has a surge voltage withstand of 6 kV and insulation voltage of 690 V at pollution degree 3.

Frequently asked questions

What contactor does the 3RU7126-1KB0 mount onto?

It mounts directly onto SIRIUS S0-size contactors via the contactor mounting fastening method, forming a one-piece motor starter assembly.

MPN
3RU7126-1KB0