Siemens
Siemens 3RB Electronic Overload Relay 3–630 A | Motor Protection
Siemens 3RB Electronic Overload Relay 3–630 A | Motor Protection
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The Siemens 3RB electronic overload relay with a 3–630 A setting range protects three-phase motors against overload and phase failure. It mounts directly under the matching contactor and opens the control circuit through its NC contact when the motor current exceeds the set value, preventing winding burn-out. Several setting ranges are available under this listing.
Key features
- Adjustable current setting dial
- Phase-failure (single-phasing) protection
- Manual or automatic reset selector
- Test and stop buttons
- 1NO + 1NC auxiliary contacts for alarm and control
- Direct mounting on matching contactors
Technical specifications
| Brand | Siemens |
|---|---|
| Part number / model | 3RB |
| Device type | Electronic overload relay |
| Current setting range | 3–630 A |
| Trip class | Class 10 (10A/10E typical) |
| Phase-loss sensitivity | yes |
| Auxiliary contacts | 1NO + 1NC |
| Reset | manual / automatic |
| Standard | IEC/EN 60947-4-1 |
Available versions
Current Range: 3-12 A, 6-25 A, 12.5-50 A, 32-115 A, 50-200 A, 55-250 A, 160-630 A.
Typical applications
- Water pump and booster pump starters
- Compressors, fans and blowers
- DOL and star-delta starters
- Conveyors and industrial machines
Selection and installation tips
Choose the range so that the motor nameplate full-load current is near the middle of the range and set the dial exactly to that value. In star-delta starters installed after the main contactor, set the relay to 58 % of the motor current.
Frequently asked questions
Why does the overload relay trip?
Usually because the motor is overloaded, a phase is missing, the setting is lower than the motor current, or the motor bearings/pump are jammed. Check the current with a clamp meter before resetting.
Which contactor does it fit?
It is designed to mount directly on the contactor frame of the same series; check the frame size in the specifications.
Buy Siemens 3RB in Egypt
Order the Siemens 3RB electronic overload relay from Spark Egypt and receive a genuine product with an official tax invoice. We deliver to Cairo, Giza, New Cairo, 6th of October, Sheikh Zayed, the New Administrative Capital, Alexandria, the Delta, the Canal cities and Upper Egypt, and our engineers help contractors, installers and maintenance teams check ratings, accessories and cross-references before purchase. Request a quotation for bulk or project quantities.
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