Stamford MA327 Specification, Installation And Adjustments

General description
The MA327 is a three phase full wave, pulse width modulated
type automatic voltage regulator (AVR) and forms part of the
excitation system for a brushless generator.
Excitation power is derived from a three-phase permanent
magnet generator (PMG), to isolate the AVR control circuits
from the effects of non-linear loads and to reduce radio
frequency interference on the generator terminals. Sustained
generator short circuit current is another feature of the PMG
system.
The AVR senses the voltage on the main generator winding
and controls the power fed to the exciter stator and hence the
main rotor to maintain the generator output voltage within the
specified limits, compensating for load, speed, temperature
and power factor of the generator. Three-phase root mean
squared (RMS) sensing is employed for superior voltage
regulation.
Soft start circuitry is included to provide a smooth controlled
build up of generator output voltage.
A frequency measuring circuit continually monitors the speed
of the generator and provides under-speed protection of the
excitation system by reducing the generator output voltage
proportionally with speed below an adjustable threshold. A
further enhancement of this feature is an adjustable volts per
Hertz slope to improve engine recovery time on turbo charged
engines.
Protection circuitry is included which cuts off the excitation
power in event of over-voltage.
Excitation limiting is a standard feature allowing control over
the amount of short circuit current flowing during short circuits
of the generator output.
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 stopped.
For complete protection, a miniature circuit breaker option is
available, providing circuit isolation in the event of a short
circuit AVR power output device.
Provision is made for the connection of a remote voltage
trimmer allowing the user fine control of the g
output.
MA327 AUTOMATIC VOLTAGE
REGULATOR (AVR)
SPECIFICATION, INSTALLATION AND ADJUSTMENTS
enerators
Technical specification
Sensing input
Voltage
Frequency
Phase
Wire
Power input )
(PMG
Voltage
Frequency
Phase
Wire
Output
(limited by PMG output
Voltage
Current
Intermittent
Resistance
Regulation
(4% engine governing)
Thermal drift
0.015%V per degree centigrade
change in AVR ambient
Soft start ramp time
0.5 - 4 seconds
Typical system response
Exciter current to 97%
External voltage adjustment
+/-5% with 5 k ohm 1 watt trimmer
Under frequency protection
Set point
Slope
Max. Dwell
Unit power dissipation
30 watts max
Accessory input
+/-1 volt input = +/- 5% generator volts
Quadrature droop sensitivity
0.04 Amps for 5% droop @ pf
Excitation limit
Setting range
Over excitation protection
Setting range
Time delay
Over-volts protection
Setting range
Time delay
Circuit breaker trip coil voltage 10 to 60 V dc
Circuit breaker trip coil resistance 50 to 100 ohms
Environmental
Vibration 5-10Hz
10-100Hz
100Hz-300Hz 4.4g pk
Relative humidity 0-70c
Operating temperature
Storage temperature
Fuse rating
10 Amps 1.25ins. quick-blow ceramic CSA UL approved
Accessories are available for this AVR.
170-250 Vac max
50-60 Hz nominal
1 or 3
2 or 3
140-220 Vac max
100-120 Hz nominal
3
3
)
max 180 V dc (1800 rpm)
continuous 6 A
12 A for 10 secs
15 ohms minimum
+/- 0.5% RMS
(AVR and generator)
300 ms
97% Hz
100-300% down to 25 Hz
10 % V/ Sec. recovery
50 - 100%
60-90 V dc
inverse time
< setting = infinity
>25 % setting = 10 seconds max
250-350 volts
1 second fixed
1mm pk
50mm/sec RMS
95%
-40 to +70c
-55 to +80c