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Siemens 3RT1025-1KB40 — Contactors

Siemens SIRIUS 3RT1025-1KB40 Power Contactor, S0, 24 VDC, 7.

MPN3RT1025-1KB40

Siemens SIRIUS power contactor, size S0, 3RT1025-1KB40, 24 VDC coil, screw terminals, 7.5 kW at AC-2 400 V, snap-on DIN rail mounting.

Source DocumentedChannel stated on listing & quote
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Independent China distributor & sourcing agent· Listing updated Sep 2026

Specifications

3RT1025-1KB40 — Identification
ParameterValue
Contactor frame sizeS0
3RT1025-1KB40 — Ratings & Performance
ParameterValue
Rated operational current, AC-12, max.10 A
Rated operational current, AC-4 @ 400 V15.5 A
Rated value @ 400 V3 A
Rated value @ 500 V10 kW
Rated value @ 690 V11 kW
Rated value @ 230 V6 A
Rated value @ 24 V10 A
Rated value @ 60 V2 A
Rated value @ 110 V1 A
Rated value @ 220 V0.3 A
3RT1025-1KB40 — Control & Coil
ParameterValue
Control supply voltage typeDC
3RT1025-1KB40 — Contacts & Poles
ParameterValue
Main poles3
Main NO contacts3
Auxiliary contact reliability1 faulty switching per 100 million (17 V, 1 mA)
3RT1025-1KB40 — Protection & Coordination
ParameterValue
Short-circuit coordination type 1, fusefuse gL/gG: 63 A
Short-circuit coordination type 2, fusefuse gL/gG: 25 A
Aux. switch short-circuit protection, fusefuse gL/gG: 10 A
3RT1025-1KB40 — Connection & Mounting
ParameterValue
Main circuit connectionscrew-type terminals
Aux. / control circuit connectionscrew-type terminals
Conductor cross-section, solid2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²), max. 2x (0.75 ... 4 mm²)
Conductor cross-section, solid or stranded2x (1 ... 2,5 mm²), 2x (2,5 ... 6 mm²), max. 2x 10 mm²
Conductor cross-section, finely stranded w/ ferrule2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)
Mounting methodscrew and snap-on mounting onto 35 mm standard mounting rail according to DIN EN 50022
Side-by-side mountingYes
3RT1025-1KB40 — Durability
ParameterValue
Durability (operating cycles, typ.)10 000 000
3RT1025-1KB40 — Environmental
ParameterValue
Operating temperature range-25 ... +60 °C
Installation altitude, max.2 000 m
3RT1025-1KB40 — Mechanical
ParameterValue
Width45 mm
Height88 mm
Depth101 mm

Product details

It is a current-production part, so it remains a standard BOM line item for new builds and replacements alike. The built-in varistor surge suppressor protects the coil driver from inductive kickback, so you can skip adding an external flyback diode across the coil terminals. Rated for AC-2 duty at 7.5 kW on 400 V, this contactor handles slip-ring motor starting and reversing loads where the current stays below the make/break stress of AC-3. For plugging or inching duty, the AC-4 rating of 15.5 A at 400 V gives the thermal limit for frequent reversals.

The 45 mm width and 88 mm height fit the S0 footprint, which is the standard for contactors up to about 12 A AC-3. IP20 on the front enclosure protects against finger contact inside the panel; the terminal area is IP00, meaning the wiring compartment is open to the panel environment. This is typical for panel-mounted contactors — the enclosure itself provides the final IP rating.

Main circuit terminals accept screw-clamp connections: 2x 0.5–1.5 mm² solid, 2x 0.75–2.5 mm² solid, or up to 2x 4 mm² solid. The auxiliary/control circuit terminals handle 2x 1–2.5 mm² solid or stranded, up to 2x 6 mm². AWG equivalents are listed for both circuits — main terminals take 2x 16–12 AWG, aux terminals take 2x 20–14 AWG. For Type 1 coordination (welding allowed but no fire risk), use a 63 A gL/gG fuse. These values let you size the branch circuit protection without guesswork.

For a contactor switching once per minute, that's roughly 19 years of continuous service before mechanical wear-out.

Frequently asked questions

What is the depth of this contactor?

The depth is 101 mm. This dimension, combined with the 45 mm width and 88 mm height, defines the S0 frame envelope for panel layout.

What wire sizes does the main circuit accept?

The main screw terminals accept 2x 0.5–1.5 mm² solid, 2x 0.75–2.5 mm² solid, or up to 2x 4 mm² solid. In AWG, that is 2x 16–12, 2x 14–10, or 1x 8.

What compliance documentation is available for this part?

The part carries a RoHS compliance date of July 1, 2006, covering the original EU RoHS directive. The SIRIUS series typically provides CE, UL, and CSA certifications; specific declarations are available through the manufacturer's documentation portal.

Will 3RT1025-1KB40 drop into a panel specified for 3RT1015-1BB42?

Both are S0 frame contactors with the same 45 mm width and DIN rail mounting, so the physical footprint is identical. However, the 3RT1015-1BB42 uses a 24 VAC coil, while this part uses 24 VDC — the coil driver must match the DC requirement. The terminal layout and auxiliary contact positions are the same within the S0 family.

MPN
3RT1025-1KB40