Siemens SIRIUS 3RH1921-2KA20 Lateral Auxiliary Switch Block, 2 NO, Spring-Type Terminal, for 3RT1 Contactors Original Brand New

Overview: Siemens 3RH1921-2KA20 Auxiliary Switch

The Siemens SIRIUS 3RH1921-2KA20 is a high-quality, second lateral auxiliary switch block designed for seamless integration with Siemens 3RT1 contactors (sizes S0 to S12). This essential control circuit component expands the contactor’s auxiliary contact capability, providing reliable feedback and control signals.

It features 2 normally open (NO) instantaneous contacts and utilizes fast, vibration-proof spring-type terminals for tool-free, efficient wiring. Part of the robust SIRIUS modular system, the 3RH1921-2KA20 offers simple snap-on mounting for quick installation on the side of the main contactor.

Benefit

• Reliable Control: Adds two extra normally open contacts for enhanced signaling and control circuit functionality.
• Fast, Simple Wiring: Spring-type terminals (also known as spring-loaded or push-in terminals) allow for quick, tool-free, and secure electrical connections, saving installation time.
• Easy Installation: Features a snap-on lateral mounting design for direct attachment to the 3RT1 contactor without the need for additional tools.
• Industrial Standard: Part of the proven Siemens SIRIUS modular system, ensuring high quality, consistency, and compatibility with other SIRIUS components.
• Space-Saving Design: Lateral mounting maintains a compact control panel layout compared to front-mounted options.

Function

The 3RH1921-2KA20 auxiliary switch mechanically links to the main 3RT1 contactor. When the contactor is energized and its main contacts close, the 2 NO contacts in this auxiliary block also close. These contacts are used in control circuits for:

1. Status Indication: Providing a signal (e.g., to a PLC or indicator light) that the main contactor has operated.
2. Interlocking: Creating logic for safety or sequencing (though this block is instantaneous, not a mirror contact).
3. Self-Holding Circuits: Often used to maintain the contactor’s energized state after the start button is released.

Application

This Siemens auxiliary contact block is ideal for general industrial control applications where additional contact capacity is required for Siemens 3RT1 series power contactors in machinery, automation panels, and motor control centers (MCCs). It is essential for engineers and technicians working with SIRIUS low-voltage industrial controls.

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