GE SX TRANSISTOR CONTROL IC3645SR4U404N2 User Manual

BASIC OPERATION AND FEATURES

SX TRANSISTOR CONTROL

Page 6

January 2000

Section 2. FEATURES OF SX 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 SX 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 Plug Braking

Section 2.1.3.b 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.c 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.d 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 current is less than the value

set by Function 24 and the accelerator input voltage is less

than 1 volt. It is important to note that this function is used

ARM

Figure 5