Komatsu 830E-AC Shop Manual page 414

Engine Control
This software function generates the engine speed
command. The engine electronic fuel control is
responsible for maintaining that speed.
The desired engine speed is determined according to
the system state:
Propel State: The engine speed is commanded such
that the engine supplies only as much horsepower as
is required to achieve the desired torque.
All Other States: The engine speed is a direct
function of the accelerator
constraints on the engine speed command are as
follows:
• If the truck is in NEUTRAL, the commanded
engine speed at full scale accelerator pedal will
be the engine's high idle. If the truck is not in
NEUTRAL, the maximum commanded engine
speed will be the engine's rated horsepower rpm.
This allows faster hoisting of the truck bed, if
desired.
• During retard state the engine speed command
will not be increased to support the DC link when
retard is being ramped out at low truck speeds.
However, engine speed may be increased if
needed to support the DC link during normal
retard when wheel slides are occurring.
The following constraints are applied to generating
the engine speed command during all operating
states:
• The engine speed command will always be
greater or equal to the minimum idle signal. The
TCI can request that the engine speed command
be increased by setting minimum idle.
• The engine speed command will be increased if
more alternator cooling is needed.
E2-30
pedal. Additional
Electrical Propulsion System Components
ALTERNATOR FIELD CONTROL
The alternator is controlled by controlling the
alternator field reference sent to the AFSE panel.
The desired alternator output voltage is dependent
on the system state. The PSC will command an
alternator field reference such that the desired DC
link voltage or three-phase voltage is maintained.
Desired Three-Phase Voltage
During all powered states, the three-phase line-to-
line voltage will not be allowed to drop below 444
volts. This is the minimum voltage needed to supply
the gate drive power converters.
During all powered states except retard, the DC link
voltage will represent the rectified three-phase
voltage. In this case, as long as the DC link voltage is
above 600 volts, the three-phase voltage will be
adequate.
During retard, the DC link voltage is not necessarily
related to the three-phase voltage since the motors
will be powering the DC link and reverse biasing the
rectification diodes. In this case, the control ensures
that the minimum three-phase voltage is maintained.
Desired DC Link Voltage
The desired link voltage is controlled by the
alternator during all powered states except retard.
The desired voltage is based on:
1. During propel, the desired DC link voltage will
be adjusted based on motor speed and
horsepower commanded to the inverters.
2. During retard, the DC link voltage may rise
above the rectified three-phase voltage. When
this occurs, the DC link voltage is controlled by
the retard torque command, grid resistor
command and chopper start. If conditions occur
which prevent the motors from producing power
to support the resistor grids, the alternator may
be required to supply some power. In this case,
the alternator field control will maintain at least
600 volts on the DC link.
3. During all powered states, the DC link voltage
will not be allowed to drop below 600 volts.
4. While the DC link is being powered up, the
voltage will be controlled
necessary to support the inverter self-tests.
to the levels
10/06 E02020