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PSC SOFTWARE FUNCTIONS
The operation of the AC drive system is regulated by
a software program which resides in the propulsion
system control panel's memory. The software
program also contains instructions to test and fault
isolate the system.
This section describes the PSC software program
and its functions without regard to hardware.
Input Processing
This function reads in all external inputs for use by
the PSC. The input processing function performs any
signal conditioning that is required and computes the
required derived inputs.
State Machine
As part of the total software package, a particular
group of regulatory software commands is included
called a "state machine". The state machine controls
the various functions of truck operation.
The software implements the state machine by
keeping track of which state the truck is in and which
state the truck is allowed to move into if the operator
requests a different mode of operation. Each
software state is defined as follows:
Startup/Shutdown State: The purpose of this state
is to ensure the system is in a desired known state
upon startup or shutdown. This is an unpowered
state.
NOTE: "Powered" and "unpowered" refer to the state
of the DC link. 600 volts or more equals "powered",
50 volts or less equals "unpowered".
E2-26
Test State: The purpose of this state is to provide an
environment
functionality. The test state will support a variety of
activities, including:
NOTE: The test state may be either powered or
unpowered at a given point in time, depending on
which activities are being performed.
Ready State: This is the default powered state. The
system will be in this state whenever the engine and
control system are ready to provide power, but none
is requested.
Ready state is also the state where the DC link is
discharged in preparation for shutdown, rest, or in
reaction to certain event conditions. Therefore, the
ready state should not be considered strictly a
powered state (as are propel and retard).
Rest State: The purpose of this state is to conserve
fuel while the truck idles for an extended period of
time. The rest state also provides an environment
where maintenance personnel can control the engine
without causing power to be applied to the DC link.
The rest state is an unpowered state.
Propel State: The purpose of this state is to provide
the
environment for engine-powered propulsion. This is a
powered state. The system will not be allowed to
maintain the propel state without sufficient power on
the DC link.
Retard State: This state provides the power system
configuration and overall environment for retard
functions, where energy from vehicle movement is
dissipated in the retarding grid resistors in an effort to
slow the truck. The retard state is a powered state.
Electrical Propulsion System Components
for
the
verification
• Waiting for the engine to start (if needed).
• Automatic testing on initial system startup or
following rest state.
• Application of power to the DC link.
• Externally initiated testing to clear a fault, set
temporary
variables,
purposes.
power
system
configuration
of
system
or
for
maintenance
and
overall
10/06 E02020
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