MX341 AUTOMATIC VOLTAGE
REGULATOR (AVR)
SPECIFICATION, INSTALLATION AND ADJUSTMENTS
General description
Technical specification
MX341 is a two 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 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 in 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.
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 to improve
engine recovery time on turbo charged engines. Soft start
circuitry is included to provide a smooth controlled build
up of generator output voltage.
Uncontrolled excitation is limited to a safe period by
internal shutdown of the AVR output device. This
condition remains latched until the generator has
stopped.
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
STAMFORD Power Factor controller or other external
devices with compatible output.
The AVR has the facility for droop CT connection, to allow
parallel running with other similarly equipped generators.
SENSING INPUT
Voltage
190-264V ac max, 1 phase, 2 wire
Frequency
50-60 Hz nominal
POWER INPUT (PMG)
Voltage
140-220V ac max, 3 phase, 3 wire
Current 3A/phase
Frequency
100-120 Hz nominal
OUTPUT
Voltage
max 120V dc
Current
continuous 2.7 A
Intermittent 6A for 10 secs.
Resistance
15 ohms minimum
REGULATION
+/- 1%
(see note 1)
THERMAL DRIFT
0.03%
per
o
C change in AVR ambient (note 2)
SOFT START RAMP TIME
3
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 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
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: 0.33 A
OVER EXCITATION PROTECTION
Set point
75 V dc
Time delay
10 seconds (fixed)
ENVIRONMENTAL
Vibration 20-100
Hz 50mm/sec
100Hz – 2kHz
3.3g
Operating temperature
-40 to +70
o
C
Relative Humidity 0-70
o
C
95% (see note 6)
Storage temperature
-55 to +80
o
C
NOTES
1.
With 4% engine governing.
2.
After 10 minutes.
3.
Applies to Mod status D onwards. Generator de-rate may
apply. Check with factory.
4.
Factory set, semi-sealed, jumper selectable.
5.
Any device connected to the analogue input must be fully
floating (galvanically isolated from ground), with an
insulation strength of 500V ac.
6. Non
condensing.
TD_MX341.GB_
11.06_03
