Overview
The R438 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
- ±0.5% Regulation — High-precision 3-phase voltage control
- 3-Phase Sensing — 40-150VAC input for balanced generator configurations
- 4A Continuous Output — 160VDC max for high-current excitation
- Wide Frequency — 10-100Hz for variable-speed applications
- Compact Design — Drop-in replacement for Leroy Somer systems
- LSA/TAL Compatible — LSA40, LSA42.3, TAL40, TAL42, TAL44
Technical Specifications
| Parameter | Value |
|---|---|
| Sensing Input | 40-150VAC, 3-phase |
| Frequency | 10-100 Hz |
| Output Voltage | Max 160VDC (at 120VAC input, high-current mode) |
| Output Current | Continuous 4A |
| Regulation Accuracy | <±0.5% |
| Excitation Type | Self-excited shunt |
| UF Limitation | k=1 |
| Voltage Setting Range | ±5% |
Compatibility
- Leroy Somer Alternator Series
- Compatible with: Part.: R438
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 46-47 series 100-3000kW. The most commonly used AVR for large diesel generator sets globally.
Competitors MX321 (Stamford), R450 (Leroy Somer upgrade).
| Parameter | R438 | MX321 | R450 |
| Brand | Leroy Somer (France) | Stamford (UK) | Leroy Somer (France) |
| Output Current | 4A cont. | 5A cont. | 6A cont. |
| Regulation | ±0.5% | ±0.5% | ±0.5% |
| Excitation Type | Self-excited | PMG | Self-excited or PMG |
| Parallel Operation | No | Native support | Yes |
| Adjustment Method | Potentiometer manual | Potentiometer manual | Digital calibration |
| Voltage Sensing | Needs R731 module | Built-in | Built-in |
| Global Installed Base | Largest (decades verified) | Large | Growing |
| Price | $200-350 + R731 $50-100 | $180-300 | $220-380 |
Selection Advice The R438 is the “gold standard” for large diesel generator AVRs. Leroy Somer LSA 46-47 series generators ship factory-equipped with R438, with decades of millions of units installed globally validating its reliability. Parts and service personnel are the most abundant worldwide. Requires the R731 voltage sensing module — an extra installation step and cost versus the MX321. If parallel operation is not needed, the R438 is the most reliable, most conservative choice (most familiar to technicians, easiest parts availability). If parallel operation is needed or simpler installation preferred (no external module), choose MX321 or R450.
