Sentry VREL-11 Voltage Relay

The Sentry VREL-11 is a compact, microprocessor‑based voltage monitoring relay designed to protect three‑phase equipment from voltage anomalies. It continuously monitors the supply voltage and trips a relay output when under‑voltage, over‑voltage, phase loss, or phase unbalance conditions are detected, preventing damage to motors, compressors, and sensitive electronics.

Technical Specifications

The device is rated for 380–480 V AC, 50/60 Hz three‑phase systems. It is housed in a DIN rail‑mountable enclosure (IP20) with screw terminals for easy wiring. An LED indicator shows relay status and fault code.

• Nominal Voltage: 380‑480 V AC, 3‑phase (50/60 Hz)

• Overvoltage Trip: 110‑130% (adjustable)

• Undervoltage Trip: 70‑90% (adjustable)

• Phase Unbalance: 5‑15% (adjustable)

• Time Delay: 0.1‑10 seconds (adjustable)

• Output Relay: 1 x SPDT, 5 A at 250 V AC (resistive)

• Power Supply: Derived from measured voltage, no external supply needed

• Mounting: DIN rail (35 mm)

• Operating Temperature: -20°C to +60°C

Application Domains

The VREL‑11 is used in motor control centers, HVAC systems, pumping stations, and industrial machinery where voltage fluctuations can cause equipment failure. Its adjustable settings allow customization for specific applications, from simple undervoltage protection to complex unbalance monitoring.

Installation and Diagnostics

Installation is straightforward with clearly labeled terminals. The relay automatically detects phase sequence and voltage presence. A fault history memory retains the last fault type, aiding troubleshooting. The VREL‑11 meets CE and UL standards, ensuring compliance for global use.