Detail

Description

The Stamford MX341 is a two-phase sensed Automatic Voltage Regulator (AVR) integral to the excitation system of brushless generators. It derives excitation power from a three-phase Permanent Magnet Generator (PMG), ensuring isolation from non-linear loads and minimizing radio frequency interference at the generator terminals. This configuration also provides sustained short-circuit current capability.

Key Features:

Voltage Regulation: Maintains generator output voltage within specified limits by controlling the power supplied to the exciter stator, compensating for variations in load, speed, temperature, and power factor.

Soft Start Functionality: Incorporates soft start circuitry to ensure a smooth and controlled build-up of generator output voltage during startup.

Under-Frequency Protection: Continuously monitors generator shaft speed, providing under-speed protection by proportionally reducing output voltage below a preset threshold. An adjustable volts-per-hertz slope enhances engine recovery time, particularly beneficial for turbocharged engines.

Over-Excitation Protection: Limits uncontrolled excitation by internally shutting down the AVR output device after a safe period, with the condition remaining latched until the generator is stopped.

Remote Voltage Adjustment: Allows connection of a remote voltage trimmer, enabling fine control of the generator's output voltage.

Parallel Operation Capability: Equipped with provisions for droop Current Transformer (CT) connection, facilitating parallel operation with other similarly equipped generators.

Technical Specifications:

Sensing Input:

Voltage: 190-264V AC max, single-phase, two-wire

Frequency: 50-60 Hz nominal

Power Input (PMG):

Voltage: 140-220V AC max, three-phase, three-wire

Current: 3A per phase

Frequency: 100-120 Hz nominal

Output:

Voltage: Maximum 120V DC

Current: Continuous 2.7A; intermittent 6A for 10 seconds

Field Resistance: Minimum 15 ohms

Regulation Accuracy: ±1%

Soft Start Ramp Time: Approximately 3 seconds

Typical System Response:

AVR Response: 10 ms

Field Current to 90%: 80 ms

Machine Voltage to 97%: 300 ms

External Voltage Adjustment: ±10% with a 1 kΩ, 1-watt trimmer

Under-Frequency Protection:

Set Point: 95% Hz

Slope: 170% down to 30 Hz

Environmental Conditions:

Operating Temperature: -40°C to +70°C

Storage Temperature: -55°C to +80°C

Relative Humidity: Up to 95% at 0-70°C (non-condensing)

Vibration: 20-100 Hz at 50 mm/sec; 100 Hz – 2 kHz at 3.3g

The MX341 AVR is standard equipment for Stamford P6, P7, and S7 alternators, offering reliable voltage regulation and protection features essential for optimal generator performance.