Blog
Siemens 3RH2140-2XF40-0LA2 Specs: Railway Contactor Relay Guide
The Siemens 3RH2140-2XF40-0LA2 is a SIRIUS 3RH2 contactor relay designed for railway applications. Its key specifications include four normally open (4 NO) contacts, a 72–125 V DC control supply range, an integrated varistor for coil surge suppression, and spring-loaded terminals in S00 size. These features make it suitable for switching control signals in railway and industrial control circuits where the specified electrical and environmental requirements are met.
Siemens 3RH2140-2XF40-0LA2 Specifications
The following table summarizes the principal characteristics published for this model by Siemens.
| Specification | Details |
|---|---|
| Manufacturer | Siemens |
| Product family | SIRIUS 3RH2 |
| Complete model number | 3RH2140-2XF40-0LA2 |
| Product type | Contactor relay for railway applications |
| Contact configuration | 4 normally open (4 NO) |
| Control supply voltage | 72–125 V DC |
| Rated coil operating range | 0.7–1.25 × Us |
| Surge suppression | Integrated varistor |
| Terminal connection | Spring-loaded terminals |
| Frame size | S00 |
| Rated insulation voltage | 690 V, under the specified pollution-degree conditions |
| Rated impulse withstand voltage | 6 kV |
| Operating ambient temperature | −40°C to +70°C |
| Front and terminal protection | IP20 |
Source: Siemens Industry Mall product listing and the published technical datasheet. Always consult the latest manufacturer documentation before installation.
What Does the 3RH2140-2XF40-0LA2 Do?
A contactor relay switches electrical control signals through its contacts when the coil is energized. Unlike a power contactor intended for switching motor loads, a contactor relay is generally selected for control-circuit duties, such as transmitting commands or switching auxiliary signals.
The 3RH2140-2XF40-0LA2 provides four normally open contacts. These contacts close when the relay operates and return to their normal open state when the coil is de-energized, subject to the device’s operating condition.
In railway control equipment, this arrangement can support command distribution, status signaling, and interconnection between control circuits. The suitability of any specific circuit depends on its electrical load, switching frequency, required reliability, and applicable railway standards.
Why the Coil Voltage and Contact Configuration Matter
72–125 V DC control supply
The specified DC control voltage range is a critical selection parameter. The relay’s coil must operate within the manufacturer’s stated limits, and the actual supply voltage should be checked under both normal and transient conditions.
Do not select this model solely because the existing system uses DC power. A 24 V DC or 48 V DC control circuit does not match the stated 72–125 V DC range.
Four normally open contacts
The 4 NO arrangement is appropriate when four normally open switching paths are required. If the existing circuit needs normally closed contacts or a mixed NO/NC arrangement, this model may not provide the required contact logic.
Integrated varistor and spring-loaded terminals
The integrated varistor suppresses voltage transients generated by the DC coil when it switches off. This helps limit coil-related voltage spikes, although the complete circuit may still require other protection measures.
Spring-loaded terminals provide a screwless connection method. During replacement, confirm the specified conductor type, wire preparation, terminal capacity, and installation procedure in the manufacturer’s instructions.
Railway and Industrial Control Applications
The model is specifically designated for railway applications. Its published temperature range and railway-oriented design make it worth evaluating for control panels and auxiliary control circuits operating in demanding environments.
- Railway control panels: Switching control signals and auxiliary circuits.
- Vehicle electrical systems: Relay functions in applications where the specified coil voltage and contact arrangement match the circuit design.
- Industrial control cabinets: Switching control signals where the electrical ratings and environmental conditions are suitable.
- Equipment monitoring circuits: Transferring discrete signals between control devices, subject to circuit requirements.
These are application areas to evaluate, not a guarantee of suitability for every railway or industrial installation. System-level approval, environmental qualification, and safety requirements must be assessed separately.
How to Check a Replacement for 3RH2140-2XF40-0LA2
When sourcing a replacement, verify the complete part number rather than relying on the SIRIUS family name or physical resemblance.
- Confirm the coil supply: Check that the control circuit falls within 72–125 V DC.
- Verify contact logic: Confirm that four normally open contacts meet the circuit diagram’s requirements.
- Check terminal compatibility: Review the spring-loaded connection design, conductor requirements, and available mounting space.
- Review environmental conditions: Confirm operating temperature, vibration and shock requirements, enclosure conditions, and relevant railway specifications.
- Validate the full order number: Compare the existing device label with the manufacturer’s current documentation before ordering.
A related product in the Siesource catalogue is the Siemens 3RT6015-1AN21 power contactor. It belongs to the broader SIRIUS contactor portfolio, but it is a different product type and should not be treated as a direct replacement for this railway contactor relay.
You can also browse Siesource’s Siemens low-voltage control and distribution products to review related control components. If you need a quotation for the exact 3RH2140-2XF40-0LA2, provide the complete part number, required quantity, and application details so the specification can be checked before purchase.
Conclusion
The Siemens 3RH2140-2XF40-0LA2 is a railway contactor relay with four normally open contacts, a 72–125 V DC coil range, an integrated varistor, and spring-loaded terminals. The most important checks are coil voltage, contact logic, connection method, and environmental requirements. Confirming these details against the original wiring and the latest Siemens datasheet helps reduce the risk of selecting an unsuitable replacement.
FAQ
What is the coil voltage of Siemens 3RH2140-2XF40-0LA2?
The specified DC control supply range is 72–125 V DC, with a rated operating range of 0.7–1.25 times the control supply reference voltage Us.
How many contacts does the 3RH2140-2XF40-0LA2 have?
It has four normally open contacts (4 NO). Check the circuit diagram to ensure this configuration matches the required switching logic.
Does the 3RH2140-2XF40-0LA2 include surge suppression?
Yes. The model has an integrated varistor for coil surge suppression. This does not automatically replace all other protection required by the application.
Can a different Siemens SIRIUS contactor replace this model?
Not automatically. Replacement suitability depends on coil voltage, contact configuration, terminal design, electrical ratings, and railway application requirements. Confirm compatibility using official Siemens documentation.