The Siemens 3RU2146-4KB0 is a SIRIUS 3RU2 thermal overload relay for motor protection, adjustable from 57 … 75 A, in size S3 for direct mounting on a SIRIUS 3RT2 contactor. It has 1 NO + 1 NC auxiliary contacts: the NC contact opens the contactor coil circuit on overload and the NO contact can signal the trip to the PLC.
At 57 … 75 A this relay suits motors of roughly 37 kW at 400 V (per the Siemens AC-3 rating), but the setting must always follow the nameplate current, not the kW value.
See our Siemens industrial controls for matching 3RT2 contactors in size S3.
Technical data
| Siemens order number | 3RU2146-4KB0 |
|---|---|
| Product | SIRIUS 3RU2 thermal overload relay |
| Size | S3 |
| Current setting range | 57 … 75 A |
| Trip class | CLASS 10 |
| Auxiliary contacts | 1 NO + 1 NC |
| Rated operating voltage | 1,000 V |
| Motor power at 400 V (approx.) | 37 kW |
| Mounting | Contactor mounting (size S3) |
| FLA, 3-phase motor at 480 V (UL) | 65 A |
| Power loss (hot, total) | 18.9 W |
| Ambient temperature (operation) | -40 … +70 °C |
| Dimensions (W x H x D) | 70 x 105 x 125 mm |
| Net weight | 0.544 kg |
| Condition | New, original Siemens |
Typical applications
- Star-delta starters (set to 0.58 x motor current in the phase leg)
- Replacement of an aged or damaged overload relay
- Pumps, fans and conveyors in water, HVAC and packaging plants
- Protection of motors with rated current 57 … 75 A
Compatibility and replacement
Plugs directly onto 3RT2 contactors of size S3 (3RT2x). For separate (stand-alone) mounting Siemens offers a terminal support. For electronic protection with a wider setting range Siemens offers the 3RB3 series.
Frequently asked questions
What motor size does it suit?
Per Siemens the range corresponds to about 37 kW at 400 V (AC-3), but always set it by the motor rated current, not by the kW rating.
How do I set it?
Turn the setting dial to the motor rated current from the nameplate, within 57 … 75 A.
Which contactor does it fit?
SIRIUS 3RT2 contactors of size S3.
Do you ship to my country, and what is the warranty?
Yes. RendatSP ships worldwide from Yiwu, China, by air in 5 to 7 days once the part is ready, and every part carries a 1-year warranty. Send the order number and quantity on WhatsApp and we will reply with a quotation.
Before you order
Compare the complete order number on the old unit with this page, including the suffix: in most ranges the last characters set the coil voltage, current range or version. If the label is worn, send us a photo and we will identify the part.
Need it fast? Send the order number, quantity and delivery country on WhatsApp or through the inquiry form and we reply with a quotation the same working day. All parts are new and original, covered by a 1-year warranty, and ship worldwide by air in 5 to 7 days once ready (shipping, payment and warranty). Local agents: Saudi Arabia, Iraq, the UAE, Egypt, Oman, Libya, Morocco, Mauritania, Yemen, Algeria and Jordan.
