Overview
The AS540 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
- Digital PID Control — Microprocessor-based regulation with ±0.5% accuracy, outperforming analog AVRs
- Closed-Loop Feedback — Continuous sensing and adjustment of alternator output voltage
- Soft Start Ramping — Adjustable voltage ramp time for smooth generator startup
- Over-Excitation Limiting — Prevents field overload and protects alternator windings
- Selectable Sensing Input — 120VAC (95-130V) or 240VAC (190-265V), 1-phase
- Under-Frequency Roll-Off — Automatic voltage reduction proportional to speed drop
- LED Status Indicators — Visual diagnostics for power, regulation, and fault conditions
Technical Specifications
| Parameter | Value |
|---|---|
| Sensing Input | 95-130VAC or 190-265VAC, 1-phase |
| Frequency | 50/60 Hz (jumper selectable) |
| Output Voltage | Max 82VDC at 200VAC input |
| Output Current | Continuous 4A, Transient 7.5A for 10 seconds |
| Regulation Accuracy | <±1% (with 4% engine governing) |
| Control Type | Microprocessor-based PID, closed-loop |
Compatibility
- Stamford HC4, HC5, HC6 Series Alternators
- Suitable for generators 30-300 kVA
- Compatible with: Part.: AS540
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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