SIEMENS
SIEMENS 3RU21261JB0 Overload Relay 7-10 A 690 V AC
Thermal overload relay protects three-phase motors at 7–10 A with automatic or manual reset up to 690 V AC
- Thermal overload protection for three-phase motors up to 10 A
- 690 V AC rating suits industrial control circuits
- Adjustable trip range from 7 A to 10 A
- Direct contactor mounting with screw terminals for quick wiring
- Auto and manual reset options reduce downtime after a fault
SIEMENS 3RU21261JB0 Overload Relay
The SIEMENS 3RU21261JB0 is a thermal overload relay designed for three-phase motor protection. It suits maintenance engineers and panel builders who need IEC-style protection for motors drawing between 7 A and 10 A. The unit mounts directly to a compatible SIRIUS S0 contactor using screw terminals. It includes the required thermal units for immediate installation.
Thermal protection and power handling
The relay operates at a maximum voltage rating of 690 V AC with a Trip Class 10 response. Its thermal overload protection type reacts to sustained overcurrent rather than momentary spikes. The adjustable current setting ranges from 7 A minimum to 10 A maximum across three poles. Auxiliary contacts provide one normally open and one normally closed circuit for status signalling.
Behaviour under sustained load
Under continuous overload the thermal elements heat progressively until the trip point is reached at Trip Class 10 timing. The relay then opens the 1NC contact and closes the 1NO contact to isolate the contactor coil. Reset type is selectable between automatic and manual modes depending on the application requirement. This makes it suitable for processes where automatic restart is unsafe.
Highlights
- Thermal overload protection for three-phase motors up to 10 A
- 690 V AC rating suits industrial control circuits
- Adjustable trip range from 7 A to 10 A
- Direct contactor mounting with screw terminals for quick wiring
- Auto and manual reset options reduce downtime after a fault
Specifications
| Brand | SIEMENS |
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Questions about this item
How do I install the 3RU21261JB0 overload relay onto a contactor, and what is the common mistake?
Mount it directly onto a compatible SIRIUS S0 contactor using the integral clips; the step often missed is fitting all three thermal units before locking the relay in place.
What maintenance or replacement will the 3RU21261JB0 need over time?
The thermal units inside the relay are the wear items; they must be replaced with the correct SIRIUS S0 set after a trip event or when calibration drifts beyond the 7–10 A range.
What limit appears first when the relay runs continuously at high load?
The thermal trip activates once the current exceeds the 10 A maximum setting for a duration defined by Trip Class 10, opening both the 1NO and 1NC auxiliary contacts.
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