AC locomotive operation with DC bus current sensor failure

Claim 1

A control system for a diesel electric locomotive of the type in which a diesel engine is connected in driving relationship to an electric power generator, power output terminals of the generator being connected to input terminals of an alternating current (AC) to direct current (DC) power converter and output terminals of the power converter being connected to relatively positive and relatively negative DC buses, a plurality of DC to AC inverters being connected in parallel to the DC buses, a plurality of DC to AC inverters being connected in parallel to the DC buses with each of the inverters being connected for supplying controlled AC power to at least one AC electric traction motor coupled in driving relationship to wheels of the locomotive, the control system being connected for controlling the power output of the inverters in response to an operator's command and to sensed operating conditions of the locomotive and wherein one of the sensed operating conditions is power output of the converter determined by measuring the voltage between the DC buses and the current output of the converter using a series connected current monitor, the improvement comprising: means for sensing failure of the current monitor; and means responsive to a sensed failure for modifying the control system to substitute a selected value for the sensed power output of the converter, the sensed power output being combined in a feedback control loop with a signal representative of the commanded power output to produce a power error signal, the failure responsive means including switch means for interrupting the power error signal and substituting for the power error signal a signal proportional to the commanded power output signal.