Siemens 3RT2025-1BB40 SIRIUS Contactor 17 A 7.5 kW

3RT2025-1BB40 SIRIUS 3RT2 power contactor, S0 frame, 17 A at AC-3

The Siemens 3RT2025-1BB40 is a three-pole SIRIUS 3RT2 power contactor in the S0 frame size. On the Siemens datasheet it is described as: power contactor, AC-3e/AC-3, 17 A, 7.5 kW / 400 V, 3-pole, 24 V DC, auxiliary contacts: 1 NO + 1 NC, screw terminal, size: S0. It switches motor and resistive loads on 400 V networks up to 17 A in AC-3 duty and 7.5 kW per motor, and it is controlled by a 24 V DC coil. Seven Star LLC supplies the 3RT2025-1BB40 in Oman and the GCC as an independent supplier in Muscat, not affiliated with the manufacturer.

It combines the 17 A S0 power section with a 24 V DC coil, which suits PLC-driven starters where the control voltage is a DC bus.

How the 3RT2025-1BB40 number is read

The prefix 3RT2 is the product type designation printed on the datasheet for the SIRIUS power contactor family. The remainder of the number, 1BB40, identifies the coil and contact configuration of this particular variant. Rather than guess at digit positions, rely on the descriptive line above: 24 V DC coil, 1 NO + 1 NC auxiliary contact(s) fitted, screw terminals, S0 size.

3RT2025-1BB40 technical specifications

How the 3RT2025-1BB40 switches, and what its coil needs

A contactor is an electromagnetically operated switch. When voltage is applied to the A1 and A2 coil terminals, the magnet pulls the main contacts closed and lifts the three poles onto the load circuit; when the coil is de-energised, spring force opens them again. On the 3RT2025-1BB40 the coil data on the datasheet are a closing power of 5.9 W and a holding power of 5.9 W, with a closing delay of 50 to 170 ms and an opening delay of 15 to 18 ms.

The coil operating range factor is 0.8 to 1.1 times rated coil voltage, which defines the supply tolerance the coil is rated for. In cabinets fed from long cable runs or from a heavily loaded control transformer, measure coil voltage at the terminals during a motor start: a voltage dip can cause chatter, which wears the contacts quickly. The device also carries 1 NO and 1 NC auxiliary contact on the front, which are normally used for the self-holding circuit or a running signal to the PLC.

Load ratings of the 3RT2025-1BB40 by utilisation category

Contactor ratings depend on the type of load. For squirrel-cage motors under normal starting (AC-3 and AC-3e) the 3RT2025-1BB40 is rated 17 A at 400 V, 17 A at 500 V and 13 A at 690 V. For resistive and slightly inductive loads (AC-1) the datasheet gives 40 A at 40 °C ambient, falling to 35 A at 60 °C for voltages up to 690 V; if the panel runs hot, use the 60 °C figure. For heavy duty such as inching and plugging (AC-4), the rating at 400 V is 15.5 A.

The datasheet also lists performance for North American motor ratings: 10 hp at 460/480 V for a three-phase motor and a full-load current of 14 A at 480 V. Switching frequency is limited to 1,000 per hour in AC-3 and the typical mechanical life is 10,000,000 operating cycles, so the contactor is suited to frequent starts as long as thermal and contact wear limits in the manual are respected.

Where the 3RT2025-1BB40 fits: overload relays, add-ons and neighbouring contactors

The 3RT2025-1BB40 is an S0 contactor, so within the SIRIUS range it pairs with S0 overload relays and the 3RH29 front auxiliary blocks. For S0 frames, relays covered in our related catalogue entries include 3RU2126-1KB0 (thermal, 9 – 12.5 A), 3RB3026-1QB0 (electronic, 6 – 25 A) and 3RB3123-4PB0 (electronic, 1 – 4 A). For motor protection against short circuit, a 3RV2 motor starter protector can be placed upstream; the type 2 coordination fuse for this contactor is gG 25 A according to the datasheet.

Selecting the 3RT2025-1BB40: ordering checklist

• Confirm the motor rated current and starting duty: for 3RT2025-1BB40, AC-3 at 400 V is 17 A; heavy starting, frequent inching or plugging needs a derated selection from AC-4 data.
• Match the coil voltage: this variant is 24 V DC; a different control voltage means a different last group of the part number.
• Count the auxiliary contacts needed: 1 NO + 1 NC are built in; add a 3RH29 front block if more are required.
• Check the ambient temperature in the panel against -25 to +60 °C and the AC-1 derating to 35 A at 60 °C.
• Confirm that conductors fit the terminals: main circuit 1 to 10 mm² finely stranded.
• Select short-circuit protection to the datasheet coordination values, for example gG 25 A for type 2.

Installing and maintaining the 3RT2025-1BB40

The 3RT2025-1BB40 mounts by screw or by snapping onto a 35 mm DIN rail (screw and snap-on mounting onto 35 mm DIN rail according to DIN EN 60715). Overall size is 85 mm high, 45 mm wide and 107 mm deep, and the net weight is 581.68 g. The datasheet allows side-by-side mounting (lateral spacing 0 mm) and lists required clearances to grounded and live parts at the front, top and bottom, so leave those gaps when laying out the panel. Torque values for terminal screws are in the datasheet; tighten to those values and retighten after the first thermal cycle, because loose screw terminals are the main cause of hot connections.

In service, inspect the main contacts for pitting, listen for coil hum, and look at the coil voltage during starts. As the datasheet lists a mechanical life of 10,000,000 cycles for the contactor, replacement is usually driven by contact wear in electrically hard duty rather than mechanical wear.

Typical applications of the 3RT2025-1BB40 in Oman and the GCC

In Oman and the wider GCC, contactors of this size class are used for water and process pump starters, ventilation and cooling fans in plants and buildings, compressor motors, conveyors and heater banks in oil and gas, power, desalination and petrochemical facilities. Panels in the region often see high ambient temperature, dust and humidity near the coast, so the temperature range of -25 to +60 °C and the AC-1 derating at 60 °C are the first things to check, along with panel ventilation and enclosure protection. The 3RT2025-1BB40 is selected when the load is around 7.5 kW at 400 V, and is typically installed with an overload relay of the same size and a motor starter protector upstream.

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Information to send with an RFQ for the 3RT2025-1BB40

• The full part number 3RT2025-1BB40 as printed on the nameplate or in the bill of materials
• Quantity and delivery location in Oman or the GCC
• Whether the coil voltage 24 V DC matches your control supply
• Any matching overload relay, auxiliary block or surge suppressor needed
• Whether the item replaces an installed contactor and, if so, a photo of the nameplate

Documents and quotation

A copy of the Siemens datasheet for the 3RT2025-1BB40 is attached on this page, so you can check ratings, dimensions and connection data before ordering. Seven Star LLC quotes against the exact part number, because neighbouring variants differ in coil voltage, range or contact arrangement and are not interchangeable without checking.

Send the part number 3RT2025-1BB40, the quantity and the delivery point in Oman or the GCC through the RFQ form, and we will reply with availability and lead time. Seven Star LLC is an independent supplier based in Muscat and is not affiliated with the manufacturer.