Siemens 3RT2038-1KB40 Industrial Grade AC Power Contactor 24VDC 80A 3NO

The Siemens 3RT2038-1KB40 is a robust industrial-grade AC power contactor engineered for demanding electrical control applications. This IEC 60947-4-1 compliant device offers exceptional reliability with a 3NO (normally open) pole configuration, a continuous current rating of 80A, and a control circuit voltage of 24VDC. Its compact design, high switching capacity, and integrated safety features make it a premier choice for motor control, power distribution, and automation systems across various industries.

Product Specifications

| Specification          | Value                       |

| :--------------------- | :-------------------------- |

| Product Type           | AC Power Contactor          |

| Manufacturer           | Siemens                     |

| Model Number           | 3RT2038-1KB40               |

| Rated Operational Current (AC-3, 400V) | 80 A                      |

| Control Circuit Voltage | 24 VDC                      |

| Number of Poles        | 3                           |

| Pole Configuration     | 3 NO (Normally Open)        |

| Coil Type              | DC                          |

| IP Rating              | IP20                        |

| Mounting Type          | Rail-mountable, Screw-mount |

| Ambient Temperature    | -25 to +60 °C               |

| Standards Compliance   | IEC 60947-4-1               |

| Connection Type        | Spring-loaded terminal      |

Core Features & Market Positioning

The Siemens 3RT2038-1KB40 distinguishes itself through its superior thermal stability and long electrical service life, crucial for continuous industrial operations. Its direct-on-line (DOL) starting capability for motors up to 37 kW at 400V streamlines system design and reduces component count. Siemens' renowned SIVACON 3RT2 series is recognized for its compact dimensions, enabling high packing density in control cabinets, a significant advantage in space-constrained environments. The contactor's robust construction and adherence to international standards like IEC 60947-4-1 underscore its suitability for mission-critical applications where failure is not an option.

Key Application Scenarios

This 80A Siemens contactor finds extensive use in motor control circuits, acting as the primary switching element for starting, stopping, and reversing three-phase induction motors. It is a staple in building automation for controlling HVAC systems, pumps, and fans, ensuring efficient operation and energy management. In industrial manufacturing, the 3RT2038-1KB40 is deployed in conveyor systems, machine tools, and process control loops where reliable power switching is paramount. Its 24VDC coil voltage makes it ideal for integration into low-voltage control systems and battery-powered applications.

Practical System Integration Guidance

Integrating the Siemens 3RT2038-1KB40 into an electrical system is straightforward due to its standardized DIN rail mounting and accessible spring-loaded terminals. For motor control, it is typically wired in series with the motor windings, with control signals from a PLC or control relay energizing the 24VDC coil to close the main contacts. Proper wire sizing according to the 80A rating and local electrical codes is essential for safe and efficient operation. Overload protection, usually provided by a separate thermal overload relay (e.g., Sirius 3RU or 3RB series), should always be integrated in series with the contactor to protect the motor from overcurrent conditions.

Operation and Risk Mitigation

The Siemens 3RT2038-1KB40 operates by magnetically actuating a set of contacts upon receiving a 24VDC signal to its coil. The 3NO configuration ensures that power is supplied to the load only when the coil is energized. To mitigate risks, ensure the control circuit is de-energized before performing any wiring or maintenance. Always verify that the ambient temperature remains within the specified operating range (-25 to +60 °C) to prevent overheating. While the 3RT2038-1KB40 is designed for high reliability, regular inspection of terminals for signs of wear or arcing, along with verification of coil voltage, can prevent unexpected failures.

Scalability & Long-Term Value

The SIVACON 3RT2 series, to which the 3RT2038-1KB40 belongs, offers excellent compatibility with other Siemens automation components and the broader Totally Integrated Automation (TIA) portal ecosystem. This ensures seamless integration with PLCs, human-machine interfaces (HMIs), and other devices for enhanced system control and monitoring. While the 3RT2038-1KB40 is a fixed-configuration contactor, scalability in larger systems is achieved by paralleling multiple contactors or by utilizing higher-rated components from the Siemens portfolio. For enhanced digital integration, advanced versions within the Siemens industrial contactor range support communication modules for diagnostics and predictive maintenance, aligning with Industry 4.0 initiatives.

Frequently Asked Questions (FAQs)

What is the maximum motor power this Siemens 3RT2038-1KB40 contactor can control?

The Siemens 3RT2038-1KB40 is rated for AC-3 duty, suitable for controlling motor circuits. At 400V, it can reliably switch motors up to 37 kW. This makes it ideal for many industrial motor applications.

Can I use this contactor for AC control circuits or does it require DC only?

This specific model, 3RT2038-1KB40, is designed with a 24VDC coil voltage. It is not suitable for direct use with AC control voltages. You must ensure your control system provides a stable 24VDC supply.

What type of terminals does the Siemens 3RT2038-1KB40 use for connections?

The 3RT2038-1KB40 features spring-loaded terminals. These terminals offer secure connections and vibration resistance. They simplify wiring and reduce installation time compared to screw terminals.