Stamford MX341 Specification, Installation And Adjustments

GENERAL DESCRIPTION
The MX341 is a two phase sensed Automatic Voltage
Regulator (AVR) and forms part of the excitation system for a
brushless generator.
In addition to regulating the generator voltage, the AVR
circuitry includes protective features to ensure safe reliable
control of the generator. Excitation power is derived from a
permanent magnet generator (PMG) to guarantee low Radio
Frequency Interference (RFI) and immunity from thyristor type
loads.
The AVR is linked with the main stator windings and controls
the power fed to the exciter stator and hence the main rotor to
maintain the machine output voltage within the specified
limits, compensating for load, speed, temperature and power
factor of the generator.
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 underspeed protection of
the excitation system by reducing the generator output
voltage proportionally with speed below a presettable
threshold. A further enhancement of this feature is an
adjustable volts/Hz slope to improve frequency recovery time
on turbo charged engines.
Uncontrolled over excitation is limited to a safe period by
internal shutdown of the AVR output device. This condition
remains latched until the generator has been stopped.
Provision is made for the connection of a remote voltage
trimmer allowing the user fine control of the generator's
output.
Accessories are available for this AVR. Please refer to factory
for further details.
MX341 AUTOMATIC VOLTAGE
REGULATOR (AVR)
SPECIFICATION, INSTALLATION AND ADJUSTMENTS
TECHNICAL SPECIFICATION
SENSING INPUT
Voltage 170-250 V ac max
Frequency 50-60 Hz nominal
Phase 2
Wire 2
POWER INPUT (PMG)
Voltage 140-220 V ac
Current 3 A/phase
Frequency 100-120 Hz nominal
Phase 3
Wire 3
OUTPUT
Voltage max 120 V dc
Current continuous 2.7 A
Transient 6 A for 10 seconds
15 Ω minimum
Field Resistance
REGULATION (See Note 1) +/- 1%
THERMAL DRIFT
(after 10 min)
1% for 40°C change in AVR ambient
SOFT START RAMP TIME
3 seconds
TYPICAL SYSTEM RESPONSE
Field current to 90% 80ms
Machine Volts to 97% 300ms
EXTERNAL VOLTAGE ADJUSTMENT
+/- 6% with 1 K Ω trimmer
UNDER FREQUENCY PROTECTION
Set Point (see note 2) 95% Hz
Slope 100-300% down to 30 Hz
UNIT POWER DISSIPATION
12 watts maximum
ACCESSORY INPUT
+/- 1 V = +/- 5% change in output volts
QUADRATURE DROOP
Maximum sensitivity (10 Ω Burden)
0.07A for 5% droop @ 0p.f.
OVER EXCITATION PROTECTION
Set Point
Time Delay (fixed)
ENVIRONMENTAL
Vibration 20-100Hz 50mm/sec
100Hz-2 kHz 3.3g
Relative Humidity
Operating Temperature
Storage Temperature -55°C + 80°C
NOTES
1. With 4% engine governing
2. Factory set, semi-sealed, jumper selectable.
75 V dc
10 seconds
0-60°C 95%
-40°C to + 70°C