BASIC OPERATION AND FEATURES
SX TRANSISTOR CONTROL
Page
10
November 2002
Coil drivers for the LINE and 1A, 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 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 2.2.5 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 down to 50 percent of a nominal battery voltage of 36-84 volts, and 75 percent of a
nominal battery voltage of 24 volts. Lower battery voltage may cause the control to operate improperly, however, the resulting
PMT should open the Line contactor, in the event of a failure.
Section 2.3 Diagnostics
Section 2.3.1 Systems Diagnostics
The control detects the system's present operating status and can be displayed to either the Dash Display or the Handset. There
are currently over 70 status codes that are available with SX systems using Traction and Pump controls and Truck Management
Module (TMM). Along with the status code display from the TMM, the SX control is capable of reducing the current to the
motor, alerting the operator of a critical fault condition.
