Siemens 3RB3123-4QB0 SIRIUS solid-state overload relay, S0
Siemens SIRIUS 3RB3123-4QB0 solid-state overload relay, Size S0, 25 A thermal current, adjustable trip class 5E/10E/20E/30E, screw terminals, for contactor mounting.
Specifications
| Parameter | Value |
|---|---|
| Product brand name | SIRIUS |
| Product designation | solid-state overload relay |
| Frame size (overload relay) | S0 |
| Combinable contactor sizes | S0 |
| Reference code (IEC 81346-2) | F |
| Parameter | Value |
|---|---|
| Overload current setting range | 6 ... 25 A |
| Trip class | CLASS 5E, 10E, 20E and 30E adjustable |
| Overload release type | electronic |
| Parameter | Value |
|---|---|
| Rated operational current | 25 A |
| Poles (main circuit) | 3 |
| Rated operating frequency | 50 ... 60 Hz |
| Rated insulation voltage (AC, pollution degree 3) | 690 V |
| Rated value (AC-3e), max. | 690 V |
| Rated surge withstand voltage | 6 kV |
| Main current circuit | screw-type terminals |
| Power loss at rated current (hot) | 1.2 W |
| Per pole | 0.4 W |
| Parameter | Value |
|---|---|
| Auxiliary contacts: NO | 1 |
| Auxiliary contacts: NC | 1 |
| Auxiliary contacts: CO (changeover) | 0 |
| Auxiliary switch short-circuit protection (required fuse) | fuse gG: 6 A |
| Switching current at 24 V | 2 A |
| Switching current at 60 V | 0.55 A |
| Switching current at 110 V | 0.3 A |
| Switching current at 120 V | 4 A |
| Switching current at 125 V | 0.3 A |
| Switching current at 220 V | 0.11 A |
| Switching current at 230 V | 3 A |
| Parameter | Value |
|---|---|
| Mounting / fastening method | Contactor mounting |
| Mounting position | any |
| Main-circuit connector arrangement | Top and bottom |
| Auxiliary/control circuit connection type | screw-type terminals |
| Removable aux./control terminal | Yes |
| Conductor cross-section: solid | 1x (0.5 ... 4 mm²), 2x (0.5 ... 2.5 mm²) |
| Conductor cross-section: solid or stranded | 1x (0,5 ... 4 mm²), 2x (0,5 ... 2,5 mm²) |
| Conductor cross-section: finely stranded with ferrule | 1x (0.5 ... 2.5 mm²), 2x (0.5 ... 1.5 mm²) |
| Conductor range (AWG), auxiliary contacts | 1x (20 ... 14), 2x (20 ... 14) |
| Parameter | Value |
|---|---|
| Operating temperature | -25 ... +60 °C |
| Storage temperature | -40 ... +80 °C |
| Transport temperature | -40 ... +80 °C |
| Relative humidity, operating | 10 ... 95 % |
| Max. installation altitude | 2 000 m |
| Shock resistance | 15g / 11 ms |
| Parameter | Value |
|---|---|
| Width | 45 mm |
| Height | 87 mm |
| Depth | 84 mm |
Product details
Frequently asked questions
What is the 3RB3123-4QB0 used for?
It is a solid-state overload relay for motor protection, mounted directly onto an S0-frame contactor. It protects the motor against overload by monitoring current and tripping the contactor when current exceeds the set threshold for longer than the selected trip class allows.
Solid-state motor protection for S0 contactors
The 3RB3123-4QB0: It mounts directly onto the contactor (fastening method: contactor mounting), so the assembly stays within the same DIN-rail footprint as the contactor itself — no extra panel space for a separate overload block.
Trip class adjustability and motor current window
Trip class is field-adjustable across CLASS 5E, 10E, 20E, and 30E — the same relay can be set for fast tripping on a pump (5E) or slower tripping on a high-inertia fan (30E) without swapping hardware. The motor current must fall between the lower current setting value and the upper setting value x 3.5 — this defines the usable motor FLA window the relay can protect.
Screw terminals require a Pozidriv PZ2 tip with a 5 to 6 mm shaft diameter — standard electrician's screwdriver, no special tooling.
Environmental tolerance and mounting flexibility
Shock resistance is 15g / 11 ms (signaling contact in tripped position: 9g / 11 ms), and vibration resistance covers 1-6 Hz at 15 mm amplitude and 6-500 Hz at 20 m/s² over 10 cycles — this relay holds calibration on a conveyor line or a compressor skid.
This is a solid-state overload relay, not a bimetallic thermal type — it uses current measurement and an electronic trip circuit, so it provides temperature-compensated protection and adjustable trip class without heating elements.