Description

This is the Siemens SIRIUS 3RH21 contactor relay, the DC-powered version of the balanced “logic” switch. It is a compact, high-performance component designed for handling control signals and auxiliary power in industrial automation environments.

Core Specifications:

Contact Configuration: 2 NO + 2 NC (2 Normally Open and 2 Normally Closed). This balanced 50/50 split is ideal for safety interlocks, reversing logic, and status signaling (where one signal turns “on” while another turns “off”).

Control Supply Voltage: 24 V DC. This makes it directly compatible with PLC outputs and modern DC power supplies, eliminating the need for bulky control transformers.

Frame Size: S00. At just 45mm wide, it is the smallest frame in the SIRIUS modular system, designed to save valuable space on the DIN rail.

Connection Type: Screw Terminals, providing a classic, vibration-resistant, and secure connection for standard industrial wiring.

Why Choose the DC Version?

PLC Direct Drive: Because it operates on 24V DC with low power consumption, it can often be switched directly by a transistor output from a PLC.

High Switching Reliability: Engineered to handle very low currents (down to 1mA at 17V), ensuring that “logic” signals are never lost due to contact oxidation.

Integrated Protection: Most 24V DC models in the 3RH21 series feature an integrated surge suppressor (diode or varistor) to protect your sensitive electronics from inductive voltage spikes when the coil is turned off.