GAC ESD 5100 Series Speed Control Unit

• Simple Installation and Adjustment
• Isochronous, Droop, & Variable Speed Operation
• Adjustable PID
• Idle Speed Circuit
• Auxiliary Accessory Input
• 10 Amp Drive Circuit
• Inputs for Accessories
INTRODUCTION
The ESD5100 Series electronic speed device is designed
to control engine speed with fast and precise response to
transient load changes. This closed loop control, when connected
to a proportional electric actuator and supplied with
a magnetic speed sensor signal, will control a wide variety
of engines in an isochronous or droop mode. It is designed
for high reliability and built ruggedly to withstand the engine
environment.
Simplicity of installation and adjustment was foremost in the
design. Non-interacting performance controls allow near optimum
response to be easily obtained.
Other features include adjustable droop and idle operation,
inputs for accessories used in multi-engine or special applications,
protection against reverse battery voltage, transient
voltages, accidental short circuit of the actuator and fail safe
design in the event of loss of speed sensor signal or battery
supply.
DESCRIPTION
Engine speed information for the speed control unit is usually
received from a magnetic speed sensor. Any other signal-
generating device may be used provided that the generated
frequency is proportional to engine speed and meets
the voltage input and frequency range specification. The
speed sensor is typically mounted in close proximity to an
engine driven ferrous gear, usually the engine ring gear. As
the teeth of the gear pass the magnetic sensor, a signal is
generated which is proportional to engine speed.
Signal strength must be within the range of the input ampli-
fier. An amplitude of 0.5 to 50 volts RMS is required to allow
the unit to function within its design specifications. The
speed signal is applied to Terminals C and D on the ESD’s.
Between these terminals there is an input impedance of over
33,000 Ω. Terminal D is internally connected to Terminal E,
battery negative. Only one end of the cable shield should be
connected.
When a speed sensor signal is received by the ESD, the signal
is amplified and shaped by an internal circuit to provide
an analog speed signal. If the speed sensor monitor does
not detect a speed sensor signal, the output circuit on the
ESD will turn off all current to the actuator.
A summing circuit receives the speed sensor signal along
with the speed adjust set point input. The speed range has
a ratio of 9:1 and is adjusted with by the 25-turn SPEED potentiometer.
The output from the summing circuit is the input
to the dynamic control section of the speed control unit. The
dynamic control circuit, of which the GAIN and STABILITY
adjustments are part of, has a control function that will provide
isochronous and stable performance for most engine
types and fuel systems.
The ESD’s circuit is influenced by the GAIN and STABILITY
performance adjustments. The governor system sensitivity
is increased with clockwise relation of the GAIN adjustment.
The GAIN adjustment has a range of 33:1. The STABILITY
adjustment, when advanced clockwise, increases the time
rate of response of the governor system to match the various
time constants of a wide variety of engines. The ESD is
a PID device, the “D”, derivative portion can be varied when
required. (See instability section in PIB1000.)
During the engine cranking cycle, the actuator becomes fully
energized and moves to the maximum fuel position. The actuator
will remain in this state during engine cranking and
acceleration. While the engine is at steady load, the actuator
will be energized with sufficient current to maintain the governor
speed set point.
The output circuit provides switching current at a frequency
of about 500 Hz. to drive the actuator. Since the switching
frequency is well beyond the natural frequency of the actuator,
there is no visible motion of the actuator output shaft.