Description

This is the Siemens SIRIUS 3RH21 contactor relay. It is a compact, high-reliability control component designed for switching auxiliary and control circuits in industrial environments. Think of it as the “logic center” for your motor starters or PLC interfaces where space is at a premium.

Core Specifications:Contact Configuration: 3 NO + 1 NC (3 Normally Open and 1 Normally Closed). This layout is ideal for simultaneously enabling three functions while providing a single safety interlock or status feedback signal.

Control Supply Voltage: 24 V DC. Since it operates on low-voltage DC, it is perfectly suited for direct connection to PLC outputs without needing interposing relays.

Frame Size: S00. This is the smallest frame in the SIRIUS modular system, measuring only 45mm in width, allowing for high-density packing on your DIN rail.

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

Why Use This Relay?

High Switching Reliability: Specifically designed for low-power control signals (down to 1mA at 17V), ensuring your control logic doesn’t fail due to contact oxidation.

Modular Expandability: Even though it has 4 contacts, you can snap on an additional auxiliary switch block to the front if your circuit logic grows.

Global Compliance: Fully rated for international use (IEC, UL, CSA), making it a “safe bet” for machines being shipped globally.