The Siemens 3RU5146-4JB0 is a SIRIUS thermal overload relay sized for a 63 A motor circuit, with an adjustable current response value of 45 to 63 A. It mounts directly onto an S3-size contactor, so the assembly slides onto a DIN rail as a single unit. The 3-pole design handles three-phase motor loads up to 1000 V rated operating voltage, making it suitable for 400 V and 690 V distribution panels common in European and North American industrial lines.
The 63 A rated operational current is the continuous ampacity through the main circuit. The adjustable range of 45 to 63 A lets you match the relay to the motor nameplate full-load amps, so one part number covers a spread of motor sizes. The 5.7 W power loss per pole (17.1 W total at rated current) means this relay will throw some heat inside the enclosure — account for that in your thermal budget, especially if you're packing several contactor-relay pairs side by side. Screw-type terminals on both the main and auxiliary circuits accept 2× (0.5 to 1.5 mm²) solid or 2× (0.75 to 2.5 mm²) finely stranded wire for the control side, and 2× (10 AWG to 1/0 AWG) for the power side. Tightening torque is 4 to 6 N·m on the main contacts. The auxiliary contacts are rated at 1 A at 24 V, 0.22 A at 110 V, and 2 A at 230 V — enough to signal a PLC input or drop out a holding circuit. The relay operates across -20 to +70 °C ambient and survives transport down to -55 °C. It's rated for 0 to 100 % relative humidity during operation, so condensation-prone environments are fine. Shock resistance is 8g for 10 ms per IEC 60068-2-27, and surge voltage resistance is 8 kV. Insulation voltage is 1000 V at pollution degree 3, meaning it's built for the dirty, damp conditions you find in a real plant.
Mounting and Spacing
The relay mounts directly onto an S3 contactor via the contactor mounting method, so the combined assembly snaps onto a DIN rail as one piece. The mounting position allows ±135° rotation and ±45° tilt forward and back from the vertical — useful for tight panel layouts. Required spacing to grounded parts at the side is 6 mm. Dimensions are 70 mm wide, 120 mm high, and 140 mm deep.