Siemens 3RT25261BB40 S0 Contactor
Application Context
The 3RT25261BB40 occupies the motor branch position in AC-3 duty applications, providing the switching element between the thermal overload relay and the motor. Its four-pole 2NO/2NC contact configuration serves both power switching and auxiliary signaling paths in the same device.
Key Parameters
| Parameter | Value |
|---|---|
| Base Product Number | 3RT2526 |
| Coil Voltage | 24 VDC |
| Must Operate Voltage | 19.2 VDC |
| Coil Power | 5.9 W |
| Coil Current | 245.8 mA |
| Coil Resistance | 97.6 Ω |
| Contact Rating | 25 A |
| Contact Form | 4PST-2NO/2NC (2 Form A, 2 Form B) |
| Mounting | Chassis Mount, DIN Rail |
| Package | Bulk |
Selection Trade-offs
- Coil voltage class: The 24 VDC coil aligns with common control voltages in DC-distributed control systems; the must-operate threshold of 19.2 VDC provides 20% drop-out margin.
- Contact arrangement: 2NO/2NC permits one pole pair for the motor branch and one pole pair for auxiliary status indication without external add-on blocks.
- Power dissipation: The 5.9 W coil load draws approximately 246 mA at rated coil voltage—factor this into control power supply sizing when multiple contactors are used in parallel.
- S0 frame size: Belongs to the Siemens Size S0 series, which determines the physical envelope and terminal layout relative to Size S00 and Size S2 siblings.
Catalog Comparison
The 3RT2526 family shares identical contact rating (25 A), pole count/form (4PST-2NO/2NC), mounting (DIN rail/chassis), and base product number across the voltage range.
| Parameter | 3RT25261BB40 (seed) | 3RT25261BA40 | 3RT25261BW40 | 3RT25261AB00 |
|---|---|---|---|---|
| Coil Voltage | 24 VDC | 12 VDC | 48 VDC | 24 VAC |
| Must Operate | 19.2 VDC | 9.6 VDC | 38.4 VDC | 19.2 VAC |
| Coil Power | 5.9 W | 5.9 W | 5.9 W | 77 VA |
| Operate Time | — | 170 ms | 170 ms | 40 ms |
| Encapsulation | Bulk | Box | Box | Box |
Why the alternates resemble the seed
All catalog peers carry the same 3RT2526 base number and identical contact/pole specifications. The primary differentiating dimension across the DC-voltage row is coil voltage (12 through 230 VDC), which scales the must-operate threshold proportionally while keeping coil power constant at 5.9 W. The AC coil variant (3RT25261AB00) differs notably in coil power (77 VA vs 5.9 W) and operates approximately four times faster (40 ms vs 170 ms), reflecting the fundamental differences between AC and DC coil design.