What it is and what it protects
The 3RU5176-5HB1: The adjustable current response range is 2.8 to 4 A, which is the critical number for the buyer: set the dial to match the motor's full-load amps. This is a Class 10 relay, meaning it will trip within 10 seconds at 7.2× the current setting — standard for general-purpose motor starting where the acceleration time is under 10 seconds. Three poles for the main current circuit, covering the three phases. The description confirms it's for single mounting, with screw terminals on both the main and auxiliary circuits, and supports both manual and automatic reset modes.
Where it fits in the panel
This relay mounts directly onto a SIRIUS S12 contactor or separately on a DIN rail. The screw terminals on the main circuit handle the motor leads; the auxiliary circuit screw terminals handle the control wiring for the reset and trip-indication functions. The operating frequency is rated for 50 to 60 Hz, so it covers both common line frequencies without derating. The surge voltage resistance is rated at 8 kV, which means the relay's insulation can withstand typical switching transients in an industrial panel without flashover. Relative humidity during operation is 0 to 100 % — it handles condensing environments, though the enclosure around it should still be rated for the location. Storage temperature range is -55 to +80 °C, which covers most warehouse and transport conditions. The substance prohibitance date of 09/03/2013 confirms RoHS compliance for the EU market.
Sourcing and lifecycle posture
For a buyer filling a BOM line, the 2.8-4 A range and Class 10 trip curve are the fit confirmation points. If your motor's FLA is within that window and your starting duty is standard (not high-inertia), this relay is a direct drop-in for the S12 contactor platform.