BASIC OPERATION AND FEATURES
SX TRANSISTOR CONTROL
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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 2.1.4.b Speed Limits
This feature provides a means to control speed by limiting
motor volts utilizing three "adjustable speed limits. This
motor volt limit regulates top speed of the transistor
controller, but actual truck speed will vary at any set point
depending on the loading of the vehicle. Each speed limit
can be adjustable with the Handset using Functions 11, 12,
and 13.
Section 2.2.2 Accelerator Volts Hold Off
Section 2.1.5 Ramp Operation
This feature checks the voltage level at the accelerator
input whenever the key switch or seat switch is activated.
If, at start up, the accelerator is calling for more than 20%
of full speed, the control will not operate. This feature
assures that the control is calling for low speed operation
at start up.
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 2.2.3 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:
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
•
Look ahead
•
Look again
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.
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Automatic look again and reset
The PMT circuit will not allow the control to start under the
following conditions:
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The control monitors both armature and field FET's at
start-up and during running.
Section 2.1.6 Steer Pump Contactor Time Delay
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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.
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 2.2.4 Thermal Protector (TP)
This temperature sensitive device is mounted to the heat
sink of the power transistor (Q1). 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. As the control cools, the
thermal protector will automatically reset, returning the
control to full power.
Section 2.1.7 On-Board Coil Drivers & Internal Coil
Suppression
Coil drivers for the LINE and SP 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 2.2.5 Low Voltage
Batteries under load, particularly if undersized or more
than 80 percent discharged, will produce low voltages at
the control terminals. The SX control is designed for use
Section 2.2.1 Static Return to Off (SRO)
September 2004
