Overview
The AS440 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
- ±1% Voltage Regulation — Precise closed-loop control for stable output under varying load conditions
- Soft Start Voltage Ramping — Gradually builds excitation voltage, preventing generator shock on startup
- Under-Frequency Roll-Off Protection — Automatically reduces voltage when engine speed drops, protecting connected equipment
- Sensing Voltage Loss Protection — Shuts down excitation if sensing signal is lost, preventing over-voltage damage
- Jumper-Selectable Input — 120VAC or 240VAC sensing, adaptable to different alternator configurations
- LED Status Indicator — Visual alert for under-frequency conditions for easy diagnostics
Technical Specifications
| Parameter | Value |
|---|---|
| Sensing Input | 120VAC (95-132V) or 240VAC (190-264V), 1-phase 2-wire |
| Output Voltage | Max 90VDC at 207VAC input |
| Output Current | Continuous 4A, Intermittent 10A |
| Regulation Accuracy | <±1% |
| Soft Start | Yes |
| Under-Frequency Protection | Yes, with LED indicator |
Compatibility
- Stamford BC16, BC18 Series Alternators
- Stamford UC22, UC27 Series Alternators
- Compatible with: Part.: AS440, 45-0364
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 Stamford 200kW+ high-performance generator sets.
Competitors
| Parameter | AS440 | AS480 | AS540 |
| Output | 4A | 4A | 4A |
| Regulation | ±0.5% | ±0.5% | ±0.5% |
| Control Type | Analog | Analog (upgraded) | Digital microprocessor |
| Communication | None | None | Yes |
| 3-Phase Sensing | Yes | Yes | Yes |
| Price | $70-100 | $80-120 | $150-250 |
Selection Advice The AS series is Stamford’s high-performance line, positioned above SX and MX. The AS440 is the best-value high-performance choice — same regulation as MX341 but with more comprehensive 3-phase sensing. The AS480 is the upgraded AS440. The AS540 is the digital high-performance model with communication interfaces for SCADA integration, suitable for smart power stations. For standard high-performance needs, choose AS440. For remote monitoring, choose AS540.
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