3RH1921-1KA11 SIEMENS

3RH1921-1KA11 Siemens Basis unit

Brand：SIEMENS Model number：3RH1921-1KA11

Country of origin: Germany Product weight：0.55kg

HS code：8517623990

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Product Details：

Product Dimensions：

The 3RH1921-1KA11 is a front-mounting auxiliary contact block designed for simple, tool-free installation onto Siemens 3RT1 contactors (sizes S00 through S12) and 3RH1 contactor relays. It provides additional contacts required for complex control circuits, signal feedbacks, and electrical interlocking routines. Built with high mechanical durability, it ensures reliable switching performance even under high-frequency operation in industrial control panels.

Product Parameters

Product Brand: Siemens SIRIUS
Product Type: Auxiliary Switch Block (Front Mounting)
Contact Configuration: 1 Normally Open (1 NO) and 1 Normally Closed (1 NC)
Terminal Type: Screw terminals for secure wire connection
Rated Operational Voltage: Up to $690 \text{ VAC}$ / $240 \text{ VDC}$
Conventional Thermal Current: $10 \text{ A}$
Rated Operational Current (AC-15 at 230 V): $6 \text{ A}$
Rated Operational Current (DC-13 at 24 V): $6 \text{ A}$
Mechanical Endurance: 10 million operating cycles
Degree of Protection: IP20 (finger-safe protection for cabinet installation)
Compatible Contactors: Siemens SIRIUS 3RT1 series (sizes S00, S0, S2, S3, S6, S10, S12) and 3RH1 contactor relays

Product Advantages

A major advantage of the 3RH1921-1KA11 is its Snap-On Tool-Free Installation, which allows control panel builders to add auxiliary contacts quickly without disassembling existing wiring. Its High Switching Reliability ensures precise signal feedback to PLCs and control units, even when switching low currents. The Compact Front-Mount Design saves critical lateral space on the DIN rail, enabling high-density panel layouts. Additionally, its Mechanically Linked Contacts (mirror contacts) provide enhanced safety for fault detection in control circuits.

Important Considerations and Precautions

When installing the 3RH1921-1KA11, ensure the main contactor is completely de-energized to prevent electric shock or short circuits. Verify that the terminal screws are tightened to the specified torque to maintain proper electrical contact and prevent loose wiring in high-vibration environments. Ensure that the total current passing through the auxiliary contacts does not exceed the rated AC-15 or DC-13 operational limits to prevent premature contact welding or degradation. Always confirm compatibility with the specific generation and size of the SIRIUS contactor being used.

Product Applications

The Siemens 3RH1921-1KA11 is widely used across various industrial control and automation applications.

Motor Control Centers: Providing run/stop status feedback to PLCs or indicator lamps on control panels.
Electrical Interlocking: Preventing two contactors from energizing simultaneously in reversing starter circuits or star-delta starters.
Fault Signaling: Wiring the NC contact into alarm circuits to indicate a contactor drop-out or trip condition.
Sequence Control: Triggering secondary control processes once the main power contactor closes.
Building Automation: Interfacing HVAC motor starters with central building management systems.

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