Basler BE3-27T/59T-3A1N3 Voltage Relay
The Basler BE3-27T/59T-3A1N3, part number 9319700103, is a solid‑state dual‑function voltage relay that provides both undervoltage (27T) and overvoltage (59T) protection in a single compact unit. Designed for three‑phase systems, this relay monitors line‑to‑line and line‑to‑neutral voltages and trips when any phase voltage falls below or rises above the respective setpoints, ensuring the safety of motors, generators, and transformers.
Protection Functions
The relay incorporates two independent protection elements: undervoltage and overvoltage. Each element has its own pickup threshold, time delay, and output contact. The undervoltage function protects against brownouts and voltage sags that can cause motor overheating or instability, while the overvoltage function guards against overvoltage conditions that may damage insulation or cause core saturation. Both functions can be enabled or disabled independently.
Key Features
Three‑phase voltage sensing with phase‑loss detection.
Adjustable undervoltage pickup: 70–100 % of nominal.
Adjustable overvoltage pickup: 105–130 % of nominal.
Independent time delays: 0.1–60 seconds each.
True RMS measurement for accuracy with distorted waveforms.
Wide auxiliary supply: 24–250 VDC or 120/240 VAC.
Two SPDT output relays (one for UV, one for OV).
LED indicators for power, UV alarm, and OV alarm.
Technical Specifications
The relay operates with a nominal voltage of 100–480 VAC (line‑to‑line) at 50/60 Hz. The voltage measurement accuracy is ±1 % of the setpoint. The pickup repeatability is ±0.5 %. The time delay accuracy is ±5 % or ±50 ms, whichever is greater. The auxiliary power consumption is less than 5 VA. The output contacts are rated for 5 A at 250 VAC (resistive). The operating temperature range is -20 °C to +60 °C.
Setting and Configuration
All settings are made via front‑panel potentiometers and DIP switches. For undervoltage, set the pickup percentage using the UV knob; for overvoltage, use the OV knob. Time delays are adjusted with separate knobs. The relay also includes a hysteresis setting (adjustable) to prevent chattering near the trip point. The DIP switches allow selection of 3‑wire or 4‑wire connection and enable/disable each function.
Installation and Wiring
Mount the relay on a DIN rail or panel using the provided clips. Connect the three voltage phases (L1, L2, L3) and neutral (if 4‑wire) to the input terminals. The auxiliary supply is connected to the designated terminals. The UV and OV output contacts are wired separately to trip circuits or alarms. Ensure proper grounding of the unit and use twisted leads for voltage sensing to minimize noise.
Applications
This relay is widely used in motor control centers to prevent low‑voltage starting and overvoltage damage. It is also applied in generator protection to trip the generator for abnormal voltage conditions, and in transformer protection to avoid overfluxing or under‑voltage stress. The dual‑function design makes it a cost‑effective solution for comprehensive voltage protection.
Testing and Commissioning
Apply nominal voltage and verify the LED status. Gradually reduce the voltage to test the undervoltage function; the UV output should trip at the setpoint after the delay. Similarly, increase the voltage to test the overvoltage function. Use a stopwatch to confirm the timing. Adjust settings as needed. Record the final settings for documentation.
Maintenance
Regularly inspect the relay for dust and debris. Check terminal tightness. Re‑test the relay annually or after any system modification. The relay has no user‑serviceable parts; in case of failure, replace the entire unit.
Advantages Over Separate Relays
Combining undervoltage and overvoltage protection in one unit saves panel space, reduces wiring, and simplifies coordination. The BE3-27T/59T also offers better accuracy and faster response than electromechanical types, with the added benefit of true RMS measurement.
Compliance
The relay meets IEC 60255 and UL 508 standards. It is CE marked and RoHS compliant.
Conclusion
The Basler BE3-27T/59T-3A1N3 is a versatile and reliable voltage protection relay, offering dual functionality in a compact package. Its robust design and precise settings make it an excellent choice for modern power systems.
