Stamford AVR SX440 Automatic Voltage Regulator

Stamford AVR SX440 Automatic Voltage Regulator (Replacement)

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AS440, AS480, SX440, SX460, MX341, MX321

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General description Technical specification

SX440 Stamford AVR is a half-wave phase-controlled thyristor type Automatic Voltage Regulator (AVR) and forms part of the excitation system for a brush-less generator.

In addition to regulating the generator voltage, the AVR circuitry includes under-speed and sensing loss protection features. Excitation power is derived directly from the generator terminals.

Positive voltage build up from residual levels is ensured by the use of efficient semiconductors in the power circuitry of the AVR.

The Stamford SX440 AVR is linked with the main stator windings and the exciter field windings to provide closed loop control of the output voltage with load regulation of +/- 1.0%.

In addition to being powered from the main stator, the AVR also derives a sample voltage from the output windings for voltage control purposes. In response to this sample voltage, the AVR controls the power fed to the exciter field, and hence the main field, to maintain the machine output voltage within the specified limits, compensating for load, speed, temperature and power factor of the generator.

A frequency measuring circuit continually monitors the generator output and provides output under-speed protection of the excitation system, by reducing the output voltage proportionally with speed below a pre-settable threshold. A manual adjustment is provided for factory setting of the under frequency roll off point, (UFRO). This can easily be changed to 50 or 60 Hz in the field by pushon link selection.

Provision is made for the connection of a remote voltage trimmer, allowing the user fine control of the generator's output.

An analogue input is provided allowing connection to a Newage Power Factor controller or other external devices with compatible output.

The Stamford Automatic Voltage Regulator SX440 has the facility for droop CT connection, to allow parallel running with other similarly equipped generators.

Technical Specification:

INPUT

Voltage 190-264V ac

Frequency 50-60 Hz nominal

Phase 1

Wire 2

OUTPUT

Voltage max 90V dc at 207V ac input

Current continuous 4A dc

Intermittent 6A for 10 secs

Resistance 15 ohms minimum

REGULATION

+/- 1% (see note 1)

THERMAL DRIFT

0.04% per deg. C change in AVR ambient (note 2)

TYPICAL SYSTEM RESPONSE

AVR response 20ms

Filed current to 90% 80 ms

Machine Volts to 97% 300ms

EXTERNAL VOLTAGE ADJUSTMENT

+/-10% with 1 k ohm 1 watt trimmer (see note 3)

UNDER FREQUENCY PROTECTION

Set point 95% Hz (see note 4)

Slope 170% down to 30 Hz

UNIT POWER DISSIPATION

12 watts maximum

BUILD UP VOLTAGE

4 Volts @ AVR terminals

ANALOGUE INPUT

Maximum input +/- 5V dc (see note 5)

Sensitivity 1v for 5% Generator Volts (adjustable)

Input resistance 1k ohm

QUADRATURE DROOP INPUT

10 ohms burden

Max. sensitivity: 0.07 A for 5% droop 0PF

Max. input: 0.33A

ENVIRONMENTAL

Vibration 20-100 Hz 50mm/sec

100Hz – 2kHz 3.3g

Operating temperature -40 to +70 ℃

Relative Humidity 0-70 oC 95% (see note 6)

Storage temperature -55 to +80 ℃