Operation & Maintenance Manual Electrical
94 Book 22826226
Electrical
General Information and Operational Theory
This machine has an electronic monitor and control system to provide discharge air pressure
control and engine and package monitor functions. The system uses the WEDGE controller to
perform these functions. The electrical system connects all the necessary switches, sensors
and transducers to the WEDGE controller in order for it to perform the monitor and control
functions.
WEDGE Controller
The WEDGE controller is the heart of the machine monitor and control system. It provides data
collection, alarming and control functions for compressor operations. It is a micro controller
based unit with analog and digital inputs and outputs.
The WEDGE controller is attached to the back of the control panel. The LED annunciators are
part of the front panel of the WEDGE. They can be seen through the laminate on the front of
the control panel. The WEDGE is attached to the control panel.
The first function of the WEDGE is to scan all analog and digital inputs at a fixed time interval.
The analog values are then compared against minimum and maximum values and an ALERT
or SHUTDOWN is issued, if a value is out of range.
The second function of the WEDGE controller is machine discharge pressure control. The
WEDGE monitors the regulation system air pressure and varies the engine throttle to maintain
the setpoint discharge air pressure. The setpoint pressure is set using the regulator on the
separator tank.
The third function of the WEDGE controller is to communicate with the diesel engine via the
J1939 CAN network. The WEDGE provides the engine throttle setting to the engine controller
and retrieves diagnostic information from the engine.
A frequency throttle is used to communicate with the engine. A square wave frequency signal
from 150 Hz to 375 Hz is sent from the WEDGE controller to the engine controller. The signal
is linear from 150 Hz at engine idle to 375 Hz at maximum run speed.
Sensors and Transducers
The electronics system contains sensors and transducers that are used to collect process data
from the compressor. The temperature is measured by a thermistor. This device exhibits a
change in resistance as the temperature changes. The resistance causes an input voltage
change to the WEDGE controller input and is interpreted as a temperature change.
The electronics system also contains pressure transducers to measure process pressure
changes. These devices have an output signal of .45 VDC to 4.5 VDC, corresponding to 0 psi
and the maximum measured psi for a particular device. The maximum pressure transducer
ranges are 100 or 225 psi. The 100 and 225 psi devices are gauge pressure devices. These
are three wire devices: excitation, signal and ground (return) connections.
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