Leroy Somer AVR R731 – Three-Phase Sensing Module

The R731 is a specialized module crafted for three-phase voltage sensing and paralleling support, designed to be used alongside compatible analog AVR regulators such as the R438, R448 and R449. Its purpose is to upgrade standard single-phase sensing AVRs to full three-phase sensing — providing better protection and monitoring for critical applications. 

Key Specifications & Features:

• Voltage sensing by three 2 VA (or 24 VA depending on version) single-phase transformers. 

• Input voltage taps:

  • High voltage (400 V): 340 V ±5% to 480 V +5% 

  • Medium voltage (230 V): 200 V ±5% to 240 V +5%

  • Low voltage (110 V): 90 V ±5% to 140 V +5% 

• Voltage adjustment range using internal rheostat: ±5% (or optionally ±10% with external potentiometer) 

• Volt-droop adjustment (for paralleling): by potentiometer P2; minimum droop ~8% at 0 power factor and 1 A from CT. 

• Current sensing for paralleling CT: Nominal 1 A; Max continuous 1.3 A; Max 10-s current ~10 A.

• Designed to be installed vertically next to the main voltage regulator module. 

• Main function: Upgrade single-phase sensing AVRs to full three-phase sensing thereby improving system reliability for three-phase alternators.

Applications:
Used in three-phase generator sets, especially when accurate three-phase sensing and paralleling features are required (such as in telecom, data centers, critical installations). The R731 allows standard analog AVRs to be used in more demanding configuration without full replacement.