Method of and apparatus for controlling the operation of variable speed gearing

Claim 1

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; and the 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.

Claim 2

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; and the 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.

Claim 3

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; and the 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 in the primary circuit of said induction generator-motor 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 in the primary circuit of said induction generator-motor has not exceeded the preset value, and stopping the operation of said induction generator-motor.

Claim 4

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; and the 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 in the primary circuit of said induction generator-motor 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 in the primary circuit of said induction generator-motor has not exceeded the preset value, and stopping the operation of said induction generator-motor.

Claim 5

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; the step of cutting off the current in the secondary circuit of said induction generator-motor by blocking the power inverter control signal to said power inverter after excess current has been sensed, provided that the current value in the secondary circuit of said induction generator-motor has exceeded a preset value; the step of continuing the operation of said induction generator-motor by reactivating the power inverter control signal to said power inverter by restart, if current attenuation has been sensed, provided that the current in the secondary circuit of said induction generator-motor has dropped below a preset value; and the step of judging that it is impossible to remove a fault in said induction generator-motor or in said transmission line, if a protective element other than the excess current sensing element in the secondary circuit of said induction generator-motor has operated during said restart, or if the number of times said restart was made has exceeded a preset value, and stopping the operation of said induction generator-motor.

Claim 6

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; the step of cutting off the current in the secondary circuit of said induction generator-motor by blocking the power inverter control signal to said power inverter after excess current has been sensed, provided that the current value in the secondary circuit of said induction generator-motor has exceeded a preset value; the step of continuing the operation of said induction generator-motor by reactivating the power inverter control signal to said power inverter by restart, if current attenuation has been sensed, provided that the current in the secondary circuit of said induction generator-motor has dropped below a preset value; and the step of judging that it is impossible to remove a fault in said induction generator-motor or in said transmission line, if a protective element other than the excess current sensing element in the secondary circuit of said induction generator-motor has operated during said restart, or if the number of times said restart was made has exceeded a preset value, and stopping the operation of said induction generator-motor.

Claim 7

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; ground excess current sensing section configured to sense current at the neutral point of said main transformer and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said ground excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 8

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; ground excess current sensing section configured to sense current at the neutral point of said main transformer and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said ground excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 9

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; generator excess current sensing section configured to sense current in the primary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said generator excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 10

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; generator excess current sensing section configured to sense current in the primary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said generator excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 11

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, and the result of judgment at said fault judging section.

Claim 12

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, and the result of judgment at said fault judging section.

Claim 13

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; restart execute judging section configured to store the number of restarts of current in the secondary circuit of said induction generator-motor and judging that it is impossible to remedy the fault, provided that the number of restarts has exceeded a preset value; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, the result of judgment at said fault judging section, and the result of judgment at said restart execute judging section.

Claim 14

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; restart execute judging section configured to store the number of restarts of current in the secondary circuit of said induction generator-motor and judging that it is impossible to remedy the fault, provided that the number of restarts has exceeded a preset value; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, the result of judgment at said fault judging section, and the result of judgment at said restart execute judging section.

Claim 15

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; ground excess current sensing section configured to sense current at the neutral point of said main transformer and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said ground excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 16

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; ground excess current sensing section configured to sense current at the neutral point of said main transformer and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said ground excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 17

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; generator excess current sensing section configured to sense current in the primary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said generator excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 18

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; generator excess current sensing section configured to sense current in the primary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said generator excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 19

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, and the result of judgment at said fault judging section.

Claim 20

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, and the result of judgment at said fault judging section.

Claim 21

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; restart execute judging section configured to store the number of restarts of current in the secondary circuit of said induction generator-motor and judging that it is impossible to remedy the fault, provided that the number of restarts has exceeded a preset value; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, the result of judgment at said fault judging section, and the result of judgment at said restart execute judging section.

Claim 22

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to sense the current in the secondary circuit of said induction generator-motor and then sensing excess current, provided that the rate of change of the current value has exceeded a preset rate of change; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; restart execute judging section configured to store the number of restarts of current in the secondary circuit of said induction generator-motor and judging that it is impossible to remedy the fault, provided that the number of restarts has exceeded a preset value; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, the result of judgment at said fault judging section, and the result of judgment at said restart execute judging section.

Claim 23

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; ground excess current sensing section configured to sense current at the neutral point of said main transformer and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said ground excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 24

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; ground excess current sensing section configured to sense current at the neutral point of said main transformer and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said ground excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 25

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; generator excess current sensing section configured to sense current in the primary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said generator excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 26

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; generator excess current sensing section configured to sense current in the primary circuit of said induction generator-motor and then sensing excess current, provided that the current value has exceeded a preset value; a judging section configured to judge whether a fault occurred in said transmission line is allowed to continue or remedied, on the basis of the result of sensing excess current at said generator excess current sensing section; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section and the result of judgment at said judging section.

Claim 27

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; current attenuation sensing section conferred to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, and the result of judgment at said fault judging section.

Claim 28

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; current attenuation sensing section conferred to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, and the result of judgment at said fault judging section.

Claim 29

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; restart execute judging section configured to store the number of restarts of current in the secondary circuit of said induction generator-motor and judging that it is impossible to remedy the fault, provided that the number of restarts has exceeded a preset value; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, the result of judgment at said fault judging section, and the result of judgment at said restart execute judging section.

Claim 30

An apparatus for controlling the operation of a variable speed gearing, comprising: a power rectifier configured 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; a power inverter configured 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; a supplying section configured to supply 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; secondary circuit excess current sensing section configured to convert a conversion instruction value signal to said power inverter into a signal corresponding to the secondary current in the secondary circuit of said induction generator-motor, comparing the value of the converted signal with the effective current value in the secondary circuit of said induction generator-motor, and then sensing excess current, provided that the deviation of the value of the converted signal from the effective current value has exceeded a preset value; current attenuation sensing section configured to sense current attenuation, provided that the current value in the secondary circuit of said induction generator-motor has dropped below a preset value; fault judging section configured to judge that a fault has occurred in said induction generator-motor, provided that a protective element other than said secondary circuit excess current sensing section is in operation; restart execute judging section configured to store the number of restarts of current in the secondary circuit of said induction generator-motor and judging that it is impossible to remedy the fault, provided that the number of restarts has exceeded a preset value; and a control section configured to conduct or cut off the current in the secondary circuit of said induction generator-motor by activating or deactivating a power inverter control signal from said variable speed controller on the basis of the result of sensing excess current at said secondary circuit excess current sensing section, the result of sensing current attenuation at said current attenuation sensing section, the result of judgment at said fault judging section, and the result of judgment at said restart execute judging section.