Stamford AVR MX321 Automatic Voltage Regulator (Replacement)

We provide good quality replacement model for Stamford MX321 AVR with very reasonable price!

AS440, AS480, SX440, SX460, MX341, MX321

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General description

MX321 Voltage Regulator is a three phase sensed Automatic Voltage Regulator and forms part of the excitation system for a brush-less generator. Excitation power is derived from a three-phase permanent magnet generator (PMG), to isolate the AVR control circuits from the effects of nonlinear loads and to reduce radio frequency interference on the generator terminals. Sustained generator short circuit current is another feature of the PMG system.

The Stamford MX321 AVR senses the voltage in the main generator winding and controls the excitation to maintain the generator output voltage within the specified limits, compensating for load, speed, temperature and power factor of the generator.

Three phase RMS sensing is employed for superior voltage regulation.

Adjustable Soft start circuitry is included to provide a smooth controlled build up of generator output voltage.

A frequency measuring circuit continually monitors the shaft speed of the generator and provides under-speed protection of the excitation system by reducing the generator output voltage proportionally with speed below a pre-settable threshold. A further enhancement of this feature is an adjustable volts per Hertz slope and voltage recovery time, to improve the response of turbo charged engines.

Current limiting may be included to allow control over the amount of sustained short circuit current.

Maximum excitation is limited to a safe period by internal shutdown of the MX321 Voltage Regulator output device. This condition remains latched until the generator has stopped.

The AVR includes an over-voltage protection feature with internal shutdown of the AVR MX321 output device, plus the ability to trip an optional excitation circuit breaker if required.

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 device with compatible output.

The Stamford AVR MX321 has the facility for droop CT connection, to allow parallel running with other similarly equipped generators.

Technical specification

SENSING INPUT

Voltage 190-264V ac max, 2 or 3 phase

Frequency 50-60 Hz nominal

POWER INPUT (PMG)

Voltage 170-220V ac max, 3 phase, 3 wire

Current 3A/phase

Frequency 100-120 Hz nominal

OUTPUT

Voltage max 120V dc

Current continuous 3.7 A (see note 1)

Intermittent 6A for 10 secs.

Resistance 15 ohms minimum

REGULATION

+/- 0.5% RMS with 4% engine governing (see note 2)

THERMAL DRIFT

0.02% per deg. C change in AVR ambient (note 3)

SOFT START RAMP TIME

0.4 - 4 seconds

TYPICAL SYSTEM RESPONSE

AVR response 10 ms

Filed current to 90% 80 ms

Machine Volts to 97% 300 ms

EXTERNAL VOLTAGE ADJUSTMENT

+/-10% with 5 k ohm 1 watt trimmer (see note 4)

UNDER FREQUENCY PROTECTION

Set point 95% Hz (see note 5)

Slope 100-300% down to 30 Hz

Max. Dwell 20% volts/S recovery

UNIT POWER DISSIPATION

18 watts maximum

ANALOGUE INPUT

Maximum input +/- 5 Vdc (see note 6)

Sensitivity 1v for 5% Generator Volts (adjustable)

Input resistance 1k ohm

QUADRATURE DROOP INPUT

10 ohms burden

Max. sensitivity: 0.22 A for 5% droop 0PF

Max. input: 0.33 A

CURRENT LIMIT INPUT

10 ohms burden

Sensitivity range: 0.5 – 1A

OVER VOLTAGE DETECTOR INPUT

Set point: 300v. Time delay: 1 Sec (fixed)

CB trip coil volts: 10-30 vdc

CB trip coil resistance: 20-60 ohms

OVER EXCITATION PROTECTION

Set point 75 V dc

Time delay 8-15 seconds (fixed)

ENVIRONMENTAL

Vibration 20-100 Hz 50mm/sec

100Hz – 2kHz 3.3g

Operating temperature -40 to +700C

Relative Humidity 0-700C 95% (see note 7)

Storage temperature -55 to +800C

NOTES

1. Derate linearly from 3.7A at 50°C to 2.7A at 70°C

2. The stated voltage regulation may not be maintained in the presence of certain transmitted radio signals. Any change in regulation will fall within the limits in Criteria B of BS.EN.61000-6-2 : 2001.

3. After 10 minutes.

4. Applies to Mod status E onwards. Generator de-rate may apply. Check with factory.

5. Factory set, semi-sealed, jumper selectable.

6. Any device connected to the analogue input must be fully floating (galvanically isolated from ground), with an insulation strength of 500V ac.

7. Non condensing.