GE SX Series Installation And Operation Manual

GE SX Series Installation And Operation Manual Manual pdf 6 page image

BASIC OPERATION AND FEATURESSX TRANSISTOR CONTROL Page 6RevisedMay 2003Section 2. FEATURES OF SX FAMILY OF TRANSISTORMOTOR CONTROLLERSSection 2.1 PerformanceSection 2.1.1 Oscillator Card FeaturesSection 2.1.1.a Standard OperationWith the accelerator at maximum ohms or volts, the creepspeed can be adjusted by Function 2 of the Handset or atrimpot. The field control section allows the adjustment ofthe field weakening level in order to set the top speed of themotor. This top speed function (Minimum Field Current) isenabled when the armature current is less than the valueset by Function 24 and the accelerator input voltage is lessthan 1 volt. Top Speed can be adjusted by Function 7 of theHandset or a trimpot.The percent on-time has a range of approximately 0 to 100percent. The SX controllers operate at a constantfrequency and the percent on-time is controlled by thepulse width of the voltage / current applied to the motorcircuits.Section 2.1.1.b Creep SpeedWith the accelerator at maximum ohms or volts(approximately 3.7 to 3.5 VDC), the creep speed can beadjusted by Function 2 of the Handset. At creep speed, theON time can decrease to approximately 5%, with the OFFtime at approximately 95%. At full transistor operation, thiscondition will be reversed (short OFF time, long ON time).This variation of ON and OFF time of the oscillator variesthe voltage applied to the motor, thereby varying the speedof the motor for a given load.Section 2.1.1.c Control AccelerationThis feature allows for adjustment of the rate of time ittakes for the control to accelerate to 100% applied batteryvoltage to the motor on hard acceleration. Armature C/A isadjusted by Function 3 from 0.1 to 22 seconds.Section 2.1.2 Current LimitThis circuit monitors motor current by utilizing sensors inseries with the armature and field windings. Theinformation detected by the sensor is fed back to the cardso that current may be limited to a pre-set value. If heavyload currents are detected, this circuit overrides theoscillator and limits the average current to a value set byFunction 4 and Function 8 of the Handset. The C/L setting isbased on the maximum thermal rating of the control.Because of the flyback current through 3REC, the motorcurrent is usually greater than battery current, except at100% ON time.Section 2.1.3 BrakingSection 2.1.3.a Regenerative Braking to Zero SpeedSlow down is accomplished whenreversing direction by providing asmall amount of retarding torque fordeceleration. If the vehicle ismoving, and the directional lever ismoved from one direction to theother, the regen signal is initiated.Once the regen signal has beeninitiated, the field current isincreased (armature circuit shown inFigure 5). Armature current isregulated to the regen current limit as set by Function 9. Asthe vehicle slows down, the field current continues toincrease, and transistor Q2 begins to chop. The fieldcurrent will increase until it reaches a preset value set byFunction 10, and transistor Q2 on-time will increase until itreaches 100% on-time. Once both of the above conditionshave been met, and regen current limit can no longer bemaintained, the braking function is canceled. The fieldswill then reverse, and the control reverts back to motoring.Part of the energy produced by the motor during regen isreturned to the battery, and part is dumped in the motor asheat.Section 2.1.3.b Pedal Position Regenerative BrakingThis feature allows control of the plugging distance basedon pedal position when there has been a “directionalswitch" change. Pedal position will reduce the regenerativecurrent to the "value set by this function" as the acceleratoris returned to the creep speed position. Maximum regencurrent is obtained with the accelerator in the top speedposition.Section 2.1.3.c Auto BrakingThis feature is enabled by initiating a "neutral position"using either the directional switch or the acceleratorswitch. Once activated, Auto Braking operates similar toPedal Position Plug Braking and is adjusted by usingFunction 21 of the Handset.Section 2.1.4 Auxiliary Speed ControlSection 2.1.4.a Field WeakeningThis function allows the adjustment of the field weakeninglevel in order to set the top speed of the motor. The functionis enabled when the armature current is less than the valueset by Function 24 and the accelerator input voltage is setfor max speed. It is important to note that this function isused to optimize motor and control performance, and thissetting will be determined by GE and OEM engineers at theARMQ1Q2Figure 5