Overview
The R120 is an Automatic Voltage Regulator (AVR) that maintains the generator output voltage within precise limits by controlling the exciter field current. It continuously samples the generator output voltage and adjusts excitation to compensate for load changes, engine speed variations, and temperature drift.
Key Features
- 4A Continuous Output — 95VDC max at 240VAC, 6A intermittent for 30 seconds
- ±1% Regulation — Tight voltage control for stable generator output
- Wide Frequency Range — 20-100Hz operation
- Compact Design — Miniaturized for easy installation
- Self-Excited Shunt — Simple, reliable excitation control
- Direct OEM Replacement — Drop-in for Leroy Somer R120 systems
Technical Specifications
| Parameter | Value |
|---|---|
| Sensing Input | 240VAC RMS ±20% (190-264VAC) |
| Frequency | 20-100 Hz |
| Output Voltage | Max 95VDC at 240VAC input |
| Output Current | Continuous 4A, Intermittent 6A for 30s |
| Regulation Accuracy | <±1% |
| Excitation Type | Self-excited shunt |
| UF Limitation | k=1.2 |
| Voltage Setting Range | ±10% |
Compatibility
Compatible with Leroy Somer LSA series alternators using SHUNT excitation. Suitable for replacement on small-to-mid size generator sets.
Why Choose ZenixPower
- Tight Voltage Regulation — <±1% RMS regulation ensures stable generator output under 0-100% load transients
- Fast Response — Sub-0.5 second recovery time prevents voltage dips during motor starting and load switching
- Dual Excitation Compatibility — Self-excited shunt or PMG-powered configurations clearly labeled for correct selection
- Built-in Protections — Under-frequency roll-off, over-excitation limiting, and soft-start ramp as standard
- Drop-In Replacement — Terminal layout and mounting dimensions match STAMFORD, Leroy-Somer, Marathon, and Mecc Alte OEM AVRs
- Pre-Calibrated — Each AVR ships with factory-default potentiometer settings for immediate plug-and-play operation
Specification Comparison
Compatible Generators Leroy Somer LSA 40-42 series 5-50kW.
Competitors R150, R180 (same series upgrades).
| Parameter | R120 | R150 | R180 |
| Output Current | 4A | 6A | 6A |
| Regulation | ±1% | ±0.8% | ±0.5% |
| Circuit Type | Standard | Standard | Solid-state |
| Price | $40-70 | $50-80 | $60-100 |
Selection Advice The R120 is Leroy Somer’s smallest AVR, suitable for LSA 40 series micro to small generators. The R150 provides 2A more current and 0.2% better regulation — the most direct R120 upgrade. The R180’s solid-state design eliminates mechanical potentiometer drift for the best long-term stability. If budget allows for a small generator, the R180 is recommended.
