Patent ID: 6285533
Filing Date: 2001-09-04
Classification: H02H,H02P

Abstract:
A method of controlling the operation of a variable speed gearing, comprising:the step of causing a power rectifier to convert an alternating current of a transmission line inputted via an exciting transformer into a direct current in the presence of a power rectifier control signal from a variable speed controller;the step of causing a power inverter to convert said direct current into an alternating current of variable frequency in the presence of a power inverter control signal from said variable speed controller to produce a secondary exciting current;the step of supplying said secondary exciting current to the secondary circuit of an induction generator-motor whose primary circuit is connected to said transmission line via at least a main transformer and thereby operating said induction generator-motor at variable speed in synchronization with the alternating current on said transmission line; andthe step of, when excess current is sensed, provided that the current value in the secondary circuit of said induction generator-motor has exceeded a preset value, judging that excess current is in the secondary circuit of said induction generator-motor due to a fault in said transmission line, if excess current has been sensed, provided that the current value at the neutral point of said main transformer has exceeded a preset value, and continuing the operation of said induction generator-motor, or judging that a fault has occurred in the secondary circuit of said induction generator-motor, if excess current has not been sensed, provided that the current value at the neutral point of said main transformer has not exceeded the preset value, and stopping the operation of said induction generator-motor.