BASIC OPERATION AND FEATURES
SX TRANSISTOR CONTROL
Page 8
October 1998
Section 2.1.5 Ramp Operation
Section 2.1.5a Ramp Start
This feature provides maximum control torque to restart a
vehicle on an incline. The memory for this function is the
directional switch. When stopping on an incline, the
directional switch must be left in its original or neutral
position to allow the control to initiate full power when
restarted. The accelerator potentiometer input will
modulate ramp start current.
Section 2.1.5b Anti-Rollback
This feature provides retarding torque to limit rollback
speed in the non-travel direction when the ACC pedal is
released when stopping on a grade, or when the brake
pedal is released when starting on a grade. This feature
forces the vehicle to roll very slowly down the grade when
accelerator or brake is released. Because the vehicle can
gain significant speed during roll-back, the torque needed
to re-start on the ramp is lower than an unrestricted roll-
back speed.
Section 2.1.6 Steer Pump Contactor Time Delay
This feature provides two options for SP time delay. Option
1 provides a 0.5 to 63 second time delayed drop out of the
steer pump contactor when the Forward or Reverse
directional switch is opened. This Option 1 is overridden by
a 1.5 second time delayed drop out whenever the seat
switch is opened. Option 2 provides a 0.5 to 63 second time
delayed drop out of the SP contactor when the seat switch
is opened.
Section 2.1.7 On-Board Coil Drivers & Internal Coil
Suppression
Coil drivers for the LINE and SP or BYPASS contactors
are on-board the control card. These contactors must have
coils rated for the vehicle battery volts.
Section 2.2 System Protective Override
Section 2.2.1 Static Return to Off (SRO)
This inherent feature of the control is designed to require
the driver to return the directional lever to the neutral
position anytime he leaves the vehicle and returns.
Additionally, if the seat switch or key switch is opened, the
control shuts off and cannot be restarted until the
directional lever is returned to neutral. A time delay of
approximately 2 seconds is built into the seat switch input
to allow momentary opening of the seat switch, if a bump is
encountered.
Section 2.2.2 Accelerator Volts Hold Off
This feature checks the voltage level at the accelerator
input whenever the key switch or seat switch is activated.
If, at start up, the voltage is less than 3.0 volts, the control
will not operate. This feature assures that the control is
calling for low speed operation at start up.
Section 2.2.3 Pulse Monitor Trip (PMT)
The PMT design contains three features which shut down,
or lock out, control operation if a fault conditions occurs
that would cause a disruption of normal vehicle operation:
•
=
Look ahead
•
=
Look again
•
=
Automatic look again and reset
The PMT circuit will not allow the control to start under the
following conditions:
•
=
The control monitors both armature and field FET's at
start-up and during running.
•
=
The control will not allow the line contactor to close at
start-up, or will drop it out during running, if either the
armature or field FET's are defective, so as to cause
uncontrolled truck movement.
Section 2.2.4 lA Current Drop Out
This adjustable feature can be set to open the lA contactor
if the traction motor is subject to excessive currents. The
dropout is adjustable with Function 6 using the Handset.
Once the control has dropped out the lA contactor due to
excessive current, the directional or accelerator switch
must be returned to neutral to reset the dropout circuit and
allow the control to pick up the lA contactor again. Using
this feature may reduce the lA contactor tip life, therefore,
it should be used only where needed to protect the motor.
Section 2.2.5 Thermal Protector (TP)
This temperature sensitive device is internal to the power
transistor (Q1) module. If the transistor's temperature
begins to exceed the design limits, the thermal protector
will lower the maximum current limit, and maintain the
transistors within their temperature limits. Even at a
reduced current limit, the vehicle will normally be able to
reach sufficient speed to initiate 1A operation, thereby
allowing the control to cool. As the control cools, the
thermal protector will automatically reset, returning the
control to full power.
Section 2.2.6 Low Voltage
Batteries under load, particularly if undersized or more
than 80 percent discharged, will produce low voltages at
