AVR AS440 Stamford Automatic Voltage Regulator for Brushless Generators

AVR AS440 Stamford Voltage Regulator is an analogue automatic voltage regulator made for brushless generator excitation systems. It controls the excitation supplied to the generator field to help keep the output voltage stable.

The AS440 uses a half-wave, phase-controlled thyristor design and Surface Mount Technology (SMT). It can work with power taken from the generator stator winding or, where supported, from an auxiliary winding.

This generator voltage regulator is designed for stable operation in changing load conditions. It is supplied as standard with STAMFORD S4 and HC5 alternators and is also available as an option for UC22 and UC27 alternators.

Key Features

• Analogue automatic voltage regulator
• Self-excited AVR design
• 2-phase voltage sensing
• 50–60 Hz nominal frequency
• Sensing input selectable between 100–130 VAC or 190–264 VAC
• Power input of 100–264 VAC, single phase
• Continuous output current up to 4 A
• ±1.0% voltage regulation
• Under-frequency protection
• Remote voltage adjustment facility
• Analogue input for compatible external control devices
• Droop CT connection for generator parallel operation
• Suitable for brushless generator excitation systems

Applications

The AS440 can be used in generator sets where an automatic voltage control system is required. It is designed to control the excitation system of compatible brushless alternators.

Common applications include:

• Diesel generator sets
• Industrial power generators
• Standby generator systems
• Prime power generator sets
• Commercial power generation equipment
• Compatible STAMFORD alternators
• Generator maintenance and AVR replacement applications

Always check the alternator model, wiring, voltage range, and AVR configuration before installation.

Technical Benefits

The AS440 provides closed-loop voltage control. It continuously senses generator output and adjusts excitation to help maintain the required voltage.

Its under-frequency protection reduces excitation when generator speed falls below the selected threshold. This helps protect the excitation system during low-speed conditions.

The AVR also provides external voltage adjustment of approximately ±10% when used with the specified 1 kΩ, 1 W trimmer. A droop CT input is available for suitable generator systems that operate in parallel.

Industry Usage

This automatic voltage regulator is suitable for industrial and commercial generator applications where stable voltage control is important.

It can be used with compatible STAMFORD alternator systems in areas such as manufacturing plants, commercial buildings, construction sites, backup power systems, telecom installations, and other power-generation setups.

The exact application depends on the alternator model and excitation system.

Performance Advantages

The AS440 has a typical AVR response of about 20 ms. The field current can reach 90% in about 80 ms, while machine voltage can reach 97% in about 300 ms under the stated test conditions. It provides continuous output current up to 4 A and transient current up to 7.5 A for 10 seconds.

Its operating temperature range is specified from -40°C to +70°C, with output-current derating above 60°C. These specifications make it suitable for a range of demanding generator environments when installed according to the manufacturer's instructions.