Patent ID: 8803356

Claim:
A controller for an AC electric train, comprising: a converter that converts an AC voltage input from an AC overhead wire through a transformer, into a DC voltage; an inverter that converts a DC voltage of the converter into an AC voltage and outputs the same to an AC motor; a current detector that detects an output current of the transformer; and a control unit including a converter control device having an input connected to said current detector and being configured to output a gate enable signal for keeping the DC voltage of the converter, based on a detection current signal received from the current detector, and a power failure detector having an input connected to said current detector and being configured to detect a power failure occurring in the AC overhead wire, based on the detection current signal received from the current detector, wherein the power failure detector includes: a specific-frequency-signal calculating unit that extracts a current component corresponding to a predetermined specific-frequency set value from the received detection current signal and outputs the extracted signal as a specific-frequency current signal; a subtracter that subtracts the received detection current signal from the specific-frequency current signal and outputs a result of subtraction as a current deviation; and a power-failure detecting unit that compares the current deviation and a predetermined power-failure-detection set value with each other, and outputs a power-failure detection signal when the current deviation is greater than the power-failure-detection set value, and wherein the converter control device stops the operation of the converter by stopping the gate enable signal based on the power-failure detection signal.