BASIC OPERATION AND FEATURES
SX TRANSISTOR CONTROL
Page
5
Section 2.1.1.b Control Acceleration
This feature allows for adjustment of the rate of time it
takes for the control to accelerate to 100% applied battery
voltage to the motor on hard acceleration. Armature C/A is
adjusted by Function 3 from 0.1 to 22 seconds.
Section 2.1.2 Current Limit
This circuit monitors motor current by utilizing sensors in
series with the armature and field windings. The
information detected by the sensor is fed back to the card
so that current may be limited to a preset value. If heavy
load currents are detected, this circuit overrides the
oscillator and limits the average current to a value set by
Function 4 and Function 8 of the Handset. The C/L setting
is based on the maximum thermal rating of the control.
Because of the flyback current through 3REC, the motor
current is usually greater than battery current, except at
100% ON time.
Section 2.1.3 Regenerative Braking
Slow down is accomplished when
releasing accelerator pedal or
depressing brake pedal by providing
a regulated amount of retarding
torque for deceleration. If the vehicle
is moving, and the accelerator pedal
is released, the regen signal is
initiated. Once the regen signal has
been initiated, the field current is
increased (armature circuit shown in
Figure 5). Armature current is
regulated to the regen current limit
as set by Function 9. As the vehicle
slows down, the field current continues to increase. The
field current will increase until it reaches a preset value set
by Function 10. Once the above condition has been met,
and regen current limit can no longer be maintained, the
braking function is canceled. Part of the energy produced
by the motor during regen is returned to the battery, and
part is dumped in the motor as heat.
Section 2.1.4 Auxiliary Speed Control
Section 2.1.4.a Field Weakening
This function allows the adjustment of the field weakening
level in order to set the top speed of the motor. The
function is enabled when the armature current is less than
the value set by Function 24 and the accelerator input
voltage is greater than 2.9 volts. It is important to note that
this function is used to optimize motor and control
performance, and this setting will be determined by GE and
OEM engineers at the time of vehicle development.
This
setting must not be changed by field personnel without the
permission of the OEM.
Section 2.1.4.b Speed Limits
This feature provides a means to control speed by limiting
motor volts utilizing "adjustable speed limits", initiated by
individual limit switches. The NC switches are connected
between input points on the control card and battery
positive. The lower motor volt limit always takes priority
when more than one switch input is open. This motor volt
limit regulates top speed of the transistor controller, but
actual vehicle speed will vary at any set point depending
on the loading of the vehicle.
Section 2.1.4.c Top Speed Regulation
This feature requires a system tachometer. The standard
GE system tach is built into the motor and provides four
pulses per armature revolution. Once the control has been
calibrated to the vehicle parameters (gear ratio
and wheel rolling radius), using Function 1, speed can be
measured with a resolution of +/- 1 mph. When traveling
down an incline, if the vehicle speed increases to the
overspeed setting, the control automatically transitions to
the regen mode. The maximum incline on which the
control will be able to maintain regulation is determined by
the characteristics of the motor, the maximum regen
armature current limit setting (Function 9), and the
maximum regen field current limit setting (Function 10).
When the vehicle reaches the bottom of the incline, and
the vehicle speed decreases below the overspeed setting
on the level surface, the control automatically transitions
back to the normal running mode.
Section 2.1.5 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.
ARM
Q1
Figure 5
D2
Updated Sept 2019
