BASIC OPERATION AND FEATURES
IT400 TRANSISTOR CONTROL
Page
6
Section 2. FEATURES OF IT FAMILY OF
TRANSISTOR MOTOR CONTROLLERS
Section 2.1 Performance
Section 2.1.1 Oscillator Card Features
Section 2.1.1.a Standard Operation
With the accelerator at maximum ohms or volts, the
creep speed can be adjusted by Function 2 of the
Handset or a trimpot. The field control section allows
the adjustment of the field weakening level in order to
set the top speed of the motor. This top speed
function (Minimum Field Current) is enabled when
the armature current is less than the value set by
Function 24 and the accelerator input voltage is less
than 1 volt. Top Speed can be adjusted by Function 7
of the Handset or a trimpot.
The percent on-time has a range of approximately 0
to 100 percent. The IT controllers operate at a
constant frequency and the percent on-time is
controlled by the pulse width of the voltage / current
applied to the motor circuits.
Section 2.1.1.b Creep Speed
With the accelerator at maximum ohms or volts
(approximately 3.7 to 3.5 VDC), the creep speed can
be adjusted by Function 2 of the Handset. At creep
speed, the ON time can decrease to approximately
5%, with the OFF time at approximately 95%. At full
transistor operation, this condition will be reversed
(short OFF time, long ON time). This variation of ON
and OFF time of the oscillator varies the voltage
applied to the motor, thereby varying the speed of the
motor for a given load.
Section 2.1.1.c 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 pre-set 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 Braking
Section 2.1.3.a Regenerative Braking to Zero
Speed
Slow down is accomplished
when reversing direction by
providing a small amount of
retarding torque for deceleration.
If the vehicle is moving, and the
directional lever is moved from
one direction to the other, 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, and
transistor Q2 begins to chop. The field current will
increase until it reaches a preset value set by
Function 10, and transistor Q2 on-time will increase
until it reaches 100% on-time. Once both of the
above conditions have been met, and regen current
limit can no longer be maintained, the braking
function is canceled. The fields will then reverse, and
the control reverts back to motoring.
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 2.1.3.b Pedal Position Plug Braking
This feature allows control of the plugging distance
based on pedal position when there has been a
“directional switch" change. Pedal position will reduce
the regenerative current to the "value set by this
function" as the accelerator is returned to the creep
speed position. Maximum regen current is obtained
with the accelerator in the top speed position.
Section 2.1.3.c Auto Braking
This feature is enabled by initiating a "neutral
position" using either the directional switch or the
accelerator switch. Once activated, Auto Braking
operates similar to Pedal Position Plug Braking and
is adjusted by using Function 21 of the Handset.
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
ARM
Q1
Q2
Figure 5
November 2005
