LOAD SENSOR.-- External three-phase current
approximately 4 percent from the internal SPEED
generator load. Load sensor input transformers process
RAMP GENERATOR.-- Ramp generator A3
the current signals (expressed as a voltage level
developed across burden resistors R1-R3) and the
of the prime mover from idle to rated speed. Closing
potential signals to compute the kW load on the
the external switch or contacts connected to TB1
Opening the switch or contacts returns the unit to idle
voltage of each phase and provides a signal
speed. Front-panel screwdriver adjustments set the
representative of the kW load.
LOW SPEED SETTING and ACCELERATE RATE of
The internal LOAD GAIN potentiometer applies a
the ramp generator.
portion of the load voltage to the bridge circuit. When
MODE SWITCH.-- This switch selects either the
connected to other units through paralleling lines, the
isochronous or the droop mode of operation. This is a
bridge circuit compares this signal with that of the other
two-section ganged switch. The first section (a speed
units. This allows each unit to share equally in
switch) either connects the paralleling lines to the load
sensor (TB1-10) for isochronous operation, or it
The correcting signal of the load sensor is applied
unbalances the load sensor bridge by shunting one leg
to the summing point to provide the load control
to common (TB1-11). The second section (also a speed
function to the amplifier.
switch) connects the load sensor output (A2TB1-5) for
isochronous or droop operation. In the isochronous
MAGNETIC PICKUP/SPEED SENSOR.-- Ac
mode, the load sensor output is connected directly to the
input pulses from a magnetic pickup provide the speed
summing point. In the DROOP mode, the output is
input signal to speed sensor A4. The magnetic pickup
connected to the DROOP control potentiometer.
consists of a coil of wire wound around a permanent
magnet. This magnet pickup is mounted close to a
DROOP CONTROL.-- DROOP control A5R1
toothed gear, which is driven by the prime mover. As
biases the engine speed to decrease speed as the load
the gear teeth pass through the magnetic field produced
increases. This is accomplished by setting the external
by the permanent magnet, a step voltage (pulse) is
mode switch to DROOP. This connects the DROOP
generated in the coil of wire.
potentiometer in series with the load sensor output.
AMPLIFIER-- The output signals from the load
sensor, the speed sensor, the SPEED setting
potentiometer, and the ramp generator are applied to the
The control section consists of
summing point input of amplifier Al. Amplifier Al
amplifies the resultant input voltage to increase or
1. the SPEED setting control,
decrease fuel proportionally. Internal GAIN and
2. the ramp generator,
RESET controls determine the magnitude and the
response time of the amplifier. The complete control
3. an external mode switch,
system is a closed loop (sensors, amplifier, actuator, fuel
4. the DROOP control, and
flow, prime mover speed, sensors), and the purpose is to
match the electronic response time to the system
5. the amplifier module.
response time for stable operation.
These circuits combine to provide the control signal
to the actuator, thus controlling the speed of the prime
DETAILED CIRCUIT DESCRIPTION
SPEED SETTING CONTROL.-- The SPEED
The following sections provide a more detailed
setting control applies a variable dc voltage to the
description of the 2301 electric control circuitry. These
amplifier summing point. When a jumper wire is
detailed descriptions are keyed to the individual module
connected to TB1 terminals 20 and 21, the SPEED
schematics. The block schematic diagram, figure 9-15,
potentiometer on the panel sets the speed.
shows all the modules in relationship to one another
Disconnecting the jumper wire and connecting a 10-turn
including inputs and outputs.
100-ohm potentiometer allows external speed control of