PLUG 1980918 - Caterpillar

2.4.1: Definition
When too much power is fed to the traction motors the wheels will spin. In the following discussions the term "wheelslip" is used to describe when the wheels just start to spin, but have not yet reached a high enough speed to cause damage to the rails and wheels.Wheelslip can occur in two ways; single axle slip (differential wheelslip) and multiple axle slip (synchronous wheelslip). The electronic locomotive control system can detect both types of wheelslip and automatically reduce the power fed to the traction motors and thus eliminate the wheelslip.This requires no corrective action on the part of the locomotive operator. The throttle can be left in notch 8, even with wet or oily track conditions.2.4.2: Automatic Sanding
The electronic locomotive control system automatically triggers the locomotive's sanders when either type of wheelslip is detected. The electronic locomotive control system drives the sanders via an interface relay.The relay is energized 200 milliseconds after a wheelslip condition is first detected (if it prevails for 200 milliseconds).The relay is then cycled (one second on and one second off) until all wheelslip conditions have been corrected.If an excessive (beyond normal regulation range) wheelslip occurs, the relay is energized continuously until this condition is corrected. This is an abnormal condition which could be caused by a slipping pinion. The excitation current is set to zero and it is annunciated by a diagnostic code on the LED's on the front panel of the main electronic governor box. The trainline wheelslip signal can be triggered by a time delay relay driven from the electronic governor system's relay. It is recommended that a 1.5 second delay is used so that the trainline signal is not triggered during normal wheelslip regulation, but only when an excessive wheelslip condition has prevailed for more than approximately one second.2.4.3: Synchronous Wheelslip (Motoring Only)
The axle speed and acceleration are derived from the current and voltage feedback signals. The inferred speed is used as a feedback to regulate the speed of the slipping axles so the axles never spin fast enough to cause any damage.2.4.4: Differential Wheelslip (Motoring And Braking)
Differential wheelslip is detected by comparing the highest and lowest traction motor (or grid) currents. When the difference is excessive the locomotive electronic control system automatically reduces the current fed to the traction motors (or field current in the case of DB) and stops the slip.The method of detection has the following advantages:* It is not affected by the normal tolerances in the current measuring circuits.* It is not affected by the differences in wheel diameters.* In motoring mode it functions properly with any number of motors cutout and allows full current to the remaining motors.2.4.5: Performance
Both the synchronous and the differential wheelslip control loops provide smooth changes in tractive effort which protects the draft gear from heavy shock loads.2.5: Grid Alarms
The electronic governor system includes two alarms associated with the dynamic brake grids. These two alarms are: * Grid Over Current Alarm* Grid Cooling Fan AlarmThese functions are performed by