Siemens 3RB3123-4NB0 SIRIUS Solid-State Overload Relay, S0
Siemens SIRIUS 3RB3123-4NB0 solid-state overload relay, S0 frame size, 1.25 A rated operational current, adjustable Trip Class 5E/10E/20E/30E, contactor-mount, screw terminals.
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 | 0.32 ... 1.25 A |
| Trip class | CLASS 5E, 10E, 20E and 30E adjustable |
| Overload release type | electronic |
| Parameter | Value |
|---|---|
| Rated operational current | 1.25 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) | 0.1 W |
| Per pole | 0.03 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) |
| 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
Adjustable trip class sets the motor protection curve
The 3RB3123-4NB0 is a SIRIUS solid-state overload relay — no bimetal drift, no heater coil swaps. The trip class is field-adjustable across CLASS 5E, 10E, 20E, and 30E, so one relay covers fast-acting (pump) to slow-start (fan, flywheel) loads without stocking four separate units. The motor current window is bounded by the setting range: IMotor must sit above the lower setting value and below upper setting value × 3.5. For a 1.25 A relay, that means the motor FLA lands within the adjustment pot range; the 3.5× ceiling handles the inrush without nuisance tripping.
Panel fit — S0 frame, contactor-mount, 45 mm wide
This is a S0-size overload relay, 45 mm wide and 87 mm tall, depth 84 mm. It mounts directly onto the contactor (fastening method: contactor mounting), not on the DIN rail itself — so the panel layout needs the contactor footprint, not a separate relay slot. The Pozidriv PZ 2 screwdriver tip is what you want in the pouch — a #2 Pozidriv, not a Phillips, to avoid cam-out on the M4 main-contact screws.
Tripped message output and auxiliary contact ratings
The relay outputs a signal contact for the "tripped" message — useful for tying into a PLC input or a remote annunciator. The auxiliary contact is rated 2 A at 24 V, 4 A at 120 V, and 3 A at 230 V, so it handles standard control voltages without an interposing relay. Shock resistance is 15g / 11 ms on the main body; the signaling contact in the tripped position derates to 9g / 11 ms. Vibration per IEC 60068-2-27: 1-6 Hz at 15 mm amplitude, 6-500 Hz at 20 m/s², 10 cycles — suitable for most industrial panel environments.