Basler BE3-49R-5K5A1 Temperature Relay
The Basler BE3-49R-5K5A1 is a solid‑state temperature relay designed to monitor resistance temperature detectors (RTDs) and provide alarm or trip signals when the measured temperature exceeds the set threshold. It is part of the BE3 series, known for high accuracy and reliability in thermal protection of rotating machinery and transformers.
Measurement Principle
The relay uses a constant‑current excitation circuit to drive the RTD (typically 100 Ω platinum or 120 Ω nickel). The voltage drop across the RTD is proportional to temperature, which is compared against a user‑adjustable reference. The relay provides one or more output contacts for alarm and trip.
Key Features
RTD input compatible with Pt100, Ni120, and Cu10.
Adjustable temperature setpoint: 0–200 °C.
Adjustable time delay: 0–60 seconds.
High accuracy: ±0.5 °C.
Wide auxiliary supply: 24–250 VDC or 120/240 VAC.
Two independent output relays (SPDT) rated 5 A.
LED indication for power, alarm, and trip.
Technical Specifications
Input sensor current: 1 mA (constant). Measurement range: -20 °C to +250 °C. Resolution: 0.1 °C. Temperature coefficient: < 0.01 %/°C. The relay also includes a sensor break detection circuit that flags an open RTD as an alarm condition. Isolation between input and output is 1500 VAC.
Applications
Primarily used for monitoring stator winding and bearing temperatures in generators, motors, and pumps. It is also applied in transformer oil temperature monitoring and HVAC systems. The BE3-49R-5K5A1 is suitable for both new equipment and retrofit projects.
Installation Procedure
Mount the relay on a DIN rail or panel using the included clips. Connect the RTD leads to the input terminals; for 3‑wire RTDs, use the compensation terminals to cancel lead resistance. Connect the auxiliary supply and output contacts as required. Ensure proper grounding of the shield if shielded cable is used.
Setting and Calibration
Set the temperature setpoint using the front‑panel potentiometer or DIP switches, depending on the model variant. The time delay prevents spurious trips from transient temperature spikes. Calibration is factory‑set but can be adjusted using an external decade box that simulates RTD resistance.
Commissioning Tests
After installation, apply power and verify the LED indicators. With the RTD at room temperature, compare the displayed temperature (if available) with a calibrated thermometer. Heat the RTD (e.g., with a heat gun) and observe the relay trip at the setpoint. Adjust if necessary.
Maintenance
Inspect the RTD connections for oxidation or looseness. Re‑test the setpoint accuracy annually. Keep the relay clean and free from conductive dust. The solid‑state design provides long service life with no mechanical wear.
Benefits
Compared to bimetallic or thermocouple‑based relays, the BE3-49R-5K5A1 offers superior accuracy, stability, and immunity to electromagnetic noise. Its RTD input ensures linear response over a wide temperature range, making it ideal for critical protection applications.
Conclusion
The Basler BE3-49R-5K5A1 Temperature Relay is a precision instrument that enhances the safety and reliability of electrical machines. Its versatile features and robust construction make it a trusted choice for thermal protection worldwide.
