The Siemens 3RA2934-2B is a mechanical interlock accessory for SIRIUS 3RT20/3RT23 contactor assemblies, designed to mechanically prevent two contactors from being switched on at the same time. Siemens specifies this accessory for contactor assemblies using 3RT203, 3RT204 and 3RT244 contactors. It is a laterally mountable mechanical interlock for reversing starter applications in Size S2.
For SB Smart, this product is best positioned as a Siemens industrial electrical accessory supplied for procurement, replacement and panel-building requirements, without claiming automation integration services.
The 3RA2934-2B is part of the Siemens SIRIUS range of mechanical interlock accessories used with contactor assemblies.
A mechanical interlock is used where two contactors must operate in a mutually exclusive manner. It provides a physical blocking arrangement so that the mechanically linked contactors cannot be closed simultaneously.
Siemens identifies the exact 3RA2934-2B as a mechanical interlock for contactor assemblies using 3RT203, 3RT204 and 3RT244 contactors.
The 3RA2934-2B is intended for the 3RT23 contactor family and is used with compatible S2/S3 contactor assemblies.
This makes it suitable for applications where two contactors are arranged as an interlocked pair, particularly in reversing starter configurations. Siemens' product documentation specifies the accessory for reversing starter Size S2 and describes it as laterally mountable.
The main purpose of the 3RA2934-2B is to provide mechanical interlocking between contactors.
In a reversing motor starter, for example, two contactors are used to control opposite motor directions. Energizing both contactors simultaneously could create an incorrect switching condition.
The mechanical interlock provides an additional physical safeguard by preventing simultaneous mechanical operation.
It can therefore complement the electrical interlocking already present in a properly designed reversing starter.
Siemens includes the 3RA2934-2B in its documentation for reversing contactor assemblies. The 2025 SIRIUS IC10 catalog lists the component as the mechanical interlock for relevant 3RT203/3RT204 contactor arrangements.
Typical applications include:
Forward/reverse motor starters
Reversing contactor assemblies
Motor direction-control panels
Industrial motor-control systems
Machine tools
Conveyors
Material-handling equipment
Production machinery
Electrical control panels
The exact Siemens datasheet identifies the 3RA2934-2B as a mechanical interlock for reversing starter Size S2 that can be mounted laterally.
Lateral mounting allows the interlock to be positioned between or alongside the applicable contactor arrangement according to the Siemens assembly configuration.
The mounting arrangement should be checked against the specific contactor sizes and assembly design before installation.
Siemens specifies the following compatible contactor families for the exact accessory:
3RT203
3RT204
3RT244
The accessory is intended for compatible contactor assemblies rather than use as a standalone switching device.
For a complete motor starter, the contactor selection, mechanical interlock and electrical interlock should all be compatible.
A properly designed reversing starter commonly uses both:
Mechanical interlock:
The 3RA2934-2B physically prevents the two contactors from closing together.
Electrical interlock:
Auxiliary NC contacts are used in the control circuit to prevent the opposite contactor coil from being energized.
The Siemens IC10 catalog shows the mechanical interlock as part of reversing contactor assembly arrangements and also identifies the electrical interlocking function in complete assemblies.
Using both forms of interlocking can provide a more robust arrangement for forward/reverse motor control when correctly designed.
The exact Siemens product listing specifies a net weight of approximately 0.033 kg. The catalog packaging information gives package dimensions of approximately 71 × 90 × 23 mm.
This compact accessory is suitable for use in industrial control-panel assemblies where space and correct contactor alignment are important.
Siemens currently lists 3RA2934-2B as an Active Product (PLM PM300). The current Industry Mall listing also provides its article number and product description.
The current Siemens datasheet is dated February 6, 2026, confirming the product designation as mechanical interlock for contactor assemblies, for contactors 3RT203, 3RT204 and 3RT244.
The mechanical interlock is suitable for contactor pairs used to reverse the direction of a three-phase motor.
It can be used in motor-control assemblies where forward and reverse operation is required.
Suitable for conveyor systems requiring selectable forward and reverse motor operation.
The interlock can be incorporated into motor-control panels used for industrial material-handling equipment.
It can be used in machine-control assemblies that require electrically and mechanically interlocked contactors.
The accessory is suitable for panel builders assembling Siemens SIRIUS contactor-based motor starters.
The 3RA2934-2B is suitable for OEM equipment manufacturers, electrical panel builders, industrial maintenance teams, industrial buyers and electrical product dealers.
For SB Smart, the product is best presented as a Siemens industrial electrical accessory for supply, procurement and replacement requirements.
SB Smart can supply Siemens contactor accessories and industrial electrical components for customers across Faridabad, Delhi NCR, Gurgaon/Gurugram, Noida, Haryana, Punjab, Mumbai and other major Indian cities.
Siemens SIRIUS mechanical interlock
Article number 3RA2934-2B
Mechanical interlock for contactor assemblies
Suitable for 3RT203, 3RT204 and 3RT244
Suitable for 3RT23 contactor applications
Designed for reversing starter Size S2
Laterally mountable
Suitable for mutually interlocked contactor arrangements
Supports forward/reverse motor-starter assemblies
Compact accessory design
Net weight approximately 0.033 kg
Active Siemens product
Prevents simultaneous contactor operation: Provides a physical interlocking mechanism between compatible contactors.
Suitable for reversing starters: Designed for applications where two contactors operate alternately.
Lateral mounting: Supports suitable S2 reversing-starter arrangements.
Compatible with 3RT20 contactors: Designed specifically for specified 3RT203, 3RT204 and 3RT244 contactors.
Compact design: Suitable for industrial panel assemblies.
Improved switching safety: Adds mechanical protection alongside electrical interlocking.
Siemens SIRIUS compatibility: Designed as a dedicated accessory for compatible Siemens contactor assemblies.
Useful for replacement: Suitable for maintenance and replacement requirements where the original interlock needs to be replaced.
The Siemens 3RA2934-2B is a dedicated mechanical interlock for compatible SIRIUS 3RT20 contactor assemblies, particularly reversing starter configurations.
Its lateral mounting, S2 reversing-starter application and compatibility with 3RT203, 3RT204 and 3RT244 contactors make it a suitable accessory for forward/reverse motor-control assemblies.
For SB Smart, this accessory is relevant for customers looking to buy Siemens contactor accessories, replacement interlocks and industrial electrical components rather than automation services.
SB Smart supplies Siemens industrial electrical products and accessories across Faridabad, Gurgaon/Gurugram, Delhi NCR, Haryana, Noida, Punjab, Mumbai and other major cities across India.
Major delivery locations include:
Faridabad
Delhi
Gurgaon/Gurugram
Delhi NCR
Noida
Greater Noida
Haryana
Punjab
Mumbai
Pune
Ahmedabad
Bengaluru
Hyderabad
Chennai
Kolkata
Jaipur
Chandigarh
Lucknow
Indore
Surat
Vadodara
Nagpur
Coimbatore
And other major cities across India
The 3RA2934-2B is a Siemens mechanical interlock for contactor assemblies, designed for compatible 3RT203, 3RT204 and 3RT244 contactors.
Yes. It is used with the applicable 3RT23 contactor arrangements, including S2/S3 configurations.
Its purpose is to mechanically prevent two interlocked contactors from being closed simultaneously.
Yes. Siemens specifies the 3RA2934-2B for a reversing starter Size S2 and as a laterally mountable mechanical interlock.
Siemens specifies 3RT203, 3RT204 and 3RT244 contactors for this mechanical interlock.
No. It is a mechanical interlock. Electrical interlocking can also be implemented using suitable auxiliary contacts in the control circuit.
Yes. Siemens currently lists 3RA2934-2B as an active product.
The Siemens Industry Mall lists a net weight of approximately 0.033 kg.
It is commonly used in reversing contactor assemblies, motor-control panels, machine tools, conveyors and industrial machinery where mutually interlocked contactors are required.
SB Smart supplies Siemens industrial electrical products and accessories in India, including SIRIUS contactor accessories, mechanical interlocks and related motor-control components for industrial procurement and replacement requirements.
The Siemens 3RA29342B provides several operational and safety advantages:
By incorporating a mechanical interlock into motor control circuits, engineers can significantly improve equipment protection and system performance.
The Siemens 3RA29342B Mechanical Interlock is commonly used in:
Its robust construction and precise operation make it an important accessory for safe motor control applications.
At SB Smart (sbsmart.in), we provide genuine Siemens industrial automation and electrical products sourced through trusted supply channels. The 3RA29342B Mechanical Interlock offers dependable performance, enhanced safety, and seamless integration with Siemens SIRIUS contactors.
Whether you are building a new reversing starter panel, upgrading existing motor control equipment, or improving electrical safety within your automation system, the Siemens 3RA29342B delivers the quality, reliability, and performance expected from Siemens industrial products.
| Specification | Details |
|---|---|
| Product Name | Mechanical Interlock |
| Manufacturer | Siemens |
| Series | SIRIUS |
| Order Code | 3RA29342B |
| Product Type | Contactor Accessory |
| Accessory Type | Mechanical Interlock |
| Compatible Series | Siemens 3RT23 |
| Suitable For | 4 Pole Contactors |
| Function | Mechanical Interlocking |
| Installation Type | Between Contactors |
| Application | Reversing Starter Systems |
| Mounting Method | Direct Mechanical Coupling |
| Material | Industrial Grade Engineering Material |
| Maintenance Requirement | Low Maintenance |
| Mechanical Durability | High |
| Industrial Application | Yes |
| Brand | Siemens |
| Condition | New & Genuine Product |
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