The present invention relates to display systems and, more particularly, to a traction load meter system for use with a diesel-electric locomotive.
Diesel-electric locomotives have a diesel generator for providing direct current to a number of traction motors which function to accelerate the locomotive. The traction motors are also used for braking the locomotive. Dynamic braking is obtained by disconnecting the motors from the power line and shunting their armatures with resistor banks. These traction motors are designed to operate continuously up to a rated power current and a rated braking current. Such motors are also designed to operate at currents above these rated currents but only for a limited period of time which is dependent upon the amount that the rated current is exceeded. Continued operation of the traction motors over the rated current for longer periods of time results in an overload condition, and operation of the motors in the overload condition could result in shortening of the service life of the motors or otherwise damaging them or the resistor banks.
Heretofore, the cab of the locomotive was equipped with an analog ammeter which indicated whether the motors were in their braking mode or their power mode. The meter also had a portion for indicating that above-rated currents were being drawn by the motors and marking adjacent this above-rated portion indicating the number of minutes the motors could be operated at such above-rated currents. The locomotive engineer was thus required to note the indicated acceptable time for a given above-rated current, and to keep track of the time elapsed in order to know when an overload condition existed. The required operation upon reaching the overload condition was to reduce the current to below the maximum continuous rated current and to operate at this reduced current until the motors had sufficient time to cool down. It will be appreciated that, with the many other duties of the engineer, sometimes this record and timekeeping might be neglected.