Fuseless inverter

Claim 2

An electrical system for receiving power from a DC electricAl source comprising a static inverter means including a plurality of main semiconductor means for inverting the power and auxiliary semiconductor means for commutating off said main semiconductor means upon conduction of said auxiliary semiconductor means, sensing means for detecting an abnormality indicative of a current overload fault and producing a signal thereupon, and control means responsive to said signal for initiating current conduction upon occurrence of the fault in at least one of said auxiliary semiconductor means to complete an additional shunt current path to share current flowing to said static inverter means.

Claim 3

An electrical system for receiving power from a DC electricAl source comprising a static inverter means including a plurality of main semiconductor means for inverting the power and auxiliary semiconductor means for commutating off said main semiconductor means upon conduction of said auxiliary semiconductor means, sensing means for detecting an abnormality indicative of a current overload fault and producing a signal thereupon, and control means responsive to said signal for initiating current conduction upon occurrence of the fault in at least one of said auxiliary semiconductor means to complete an additional shunt current path to share current flowing to said static inverter means.

Claim 4

An electrical system for receiving power from a DC electricAl source comprising a static inverter means including a plurality of main semiconductor means for inverting the power and auxiliary semiconductor means for commutating off said main semiconductor means upon conduction of said auxiliary semiconductor means, sensing means for detecting an abnormality indicative of a current overload fault and producing a signal thereupon, and control means responsive to said signal for initiating current conduction upon occurrence of the fault in at least one of said auxiliary semiconductor means to complete an additional shunt current path to share current flowing to said static inverter means.

Claim 5

An electrical system as defined in claim 1 and wherein said auxiliary semiconductor means comprises commutation semiconductor means that are adapted and arranged to commutate off said main semiconductor means periodically and routinely during normal inverter operation in the absence of a fault.

Claim 6

An electrical system as defined in claim 1 and further comprising means responsive to said signal to interrupt power flow to said static inverter when said fault is present for a predetermined length of time.

Claim 7

An electrical system as defined in claim 1 and wherein said control means further comprises means responsive to said signal to initiate current conduction in addition in at least one previously non-conducting one of said main semiconductor means to share current flowing to said static inverter means.

Claim 8

An electrical system for receiving power from a DC electrical source comprising a static inverter means including a plurality of semiconductor means in which start of current conduction is controllable for inverting DC to AC, sensing means for detecting a fault and producing a signal thereupon, and control means responsive to said signal for initiating current conduction, upon occurrence of the faults, in a greater number of said semiconductor means than normally simultaneously conduct current, and wherein said plurality of semiconductor means comprises main semiconductor means for inverting the power and auxiliary semiconductor means for commutating off said main semiconductor means upon conduction of said auxiliary semiconductor means, and wherein said control means further includes means for initiating current conduction in at least one of said auxiliary semiconductor means after a time interval following initiation of conduction in those ones of said greater number that are main semiconductor means, to enable normal inverter operation to be resumed without shutdown if the fault terminates.

Claim 9

An electrical system for receiving power from a DC electrical source comprising a static inverter means including a plurality of semiconductor means in which start of current conduction is controllable for inverting DC to AC, sensing means for detecting a fault and producing a signal thereupon, and control means responsive to said signal for initiating current conduction, upon occurrence of the faults, in a greater number of said semiconductor means than normally simultaneously conduct current, and wherein said plurality of semiconductor means comprises main semiconductor means for inverting the power and auxiliary semiconductor means for commutating off said main semiconductor means upon conduction of said auxiliary semiconductor means, and wherein said control means further includes means for initiating current conduction in at least one of said auxiliary semiconductor means after a time interval following initiation of conduction in those ones of said greater number that are main semiconductor means, to enable normal inverter operation to be resumed without shutdown if the fault terminates.

Claim 10

An electrical system as defined in claim 5 and further comprising a shutdown device responsive to said signal and connected to interrupt power flow to said static inverter when said fault is present for a predetermined cumulative length of time.

Claim 11

An electrical system as defined in claim 6 and wherein said shutdown device comprises a delayed-opening contactor responsive to open when said signal has existed for said predetermined length of time.

Claim 12

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising first switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means intermediate said first switching circuit means and said static circuit means and responsive to the establishment of said shunt current to block current conduction to said static circuit mEans and responsive to the reestablishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, and further comprising shutdown means for interrupting power flow to said static circuit means when a fault persists for a predetermined time.

Claim 13

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising first switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means intermediate said first switching circuit means and said static circuit means and responsive to the establishment of said shunt current to block current conduction to said static circuit mEans and responsive to the reestablishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, and further comprising shutdown means for interrupting power flow to said static circuit means when a fault persists for a predetermined time.

Claim 14

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the re-establishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, and wherein an impedance element is connected in series intermediate the source and said semiconductor.

Claim 15

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the re-establishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, and wherein an impedance element is connected in series intermediate the source and said semiconductor.

Claim 16

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter stopping current in a conducting main semiconductor comprising first switching means connected in shunt across said input for initiating shunt current flow on the occurrence of a fault to divert current from said static circuit means, and second switching means intermediate said source and said semiconductor for blocking current flow in each said main semiconductor to render the latter non-conductive on the occurrence of a fault, said protection means including time delay means for blocking said shunt current and rendering said second switching means conductive within a first predetermined time after said shunt current is established, and in which said time delay means comprises a tank circuit including a capacitor and an inductor across said input to resonate upon a fault, and a rectifier connected across said input for recharging said capacitor and poled to block current from said source, and said protection means includes sensing means comprising voltage sensing means responsive to produce a signal upon occurrence of a voltage across said input below a predetermined level, and further comprising a slow-opening contactor connected for interrupting electrical power flow to said static circuit means and responsive to said signal to interrupt said flow after said signal exists for a second predetermined cumulative time greater than said first predetermined time.

Claim 17

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter stopping current in a conducting main semiconductor comprising first switching means connected in shunt across said input for initiating shunt current flow on the occurrence of a fault to divert current from said static circuit means, and second switching means intermediate said source and said semiconductor for blocking current flow in each said main semiconductor to render the latter non-conductive on the occurrence of a fault, said protection means including time delay means for blocking said shunt current and rendering said second switching means conductive within a first predetermined time after said shunt current is established, and in which said time delay means comprises a tank circuit including a capacitor and an inductor across said input to resonate upon a fault, and a rectifier connected across said input for recharging said capacitor and poled to block current from said source, and said protection means includes sensing means comprising voltage sensing means responsive to produce a signal upon occurrence of a voltage across said input below a predetermined level, and further comprising a slow-opening contactor connected for interrupting electrical power flow to said static circuit means and responsive to said signal to interrupt said flow after said signal exists for a second predetermined cumulative time greater than said first predetermined time.

Claim 18

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momenTarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the re-establishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, wherein said second switching means is a gatable avalanche type of semiconductor device gated off and on in response to the voltage input to said static circuit means and becoming non-conductive when the anode voltage of said device is reduced to substantially its cathode voltage upon start of said current.

Claim 19

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momenTarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the re-establishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, wherein said second switching means is a gatable avalanche type of semiconductor device gated off and on in response to the voltage input to said static circuit means and becoming non-conductive when the anode voltage of said device is reduced to substantially its cathode voltage upon start of said current.

Claim 20

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the reestablishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, and further comprising shutdown means for interrupting power flow to said static circuit means when a fault persists for a predetermined cumulative time, and wherein said shutdown means is a delayed-opening contactor in which a time delay occurs before interruption of said power flow.

Claim 21

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the reestablishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means, and further comprising shutdown means for interrupting power flow to said static circuit means when a fault persists for a predetermined cumulative time, and wherein said shutdown means is a delayed-opening contactor in which a time delay occurs before interruption of said power flow.

Claim 22

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter stopping current in a conducting main semiconductor, said protection means comprising voltage sensing means responsive to produce a signal upon occurrence of a voltage across said input below a predetermined level, said protection means further comprising first switching means connected in shunt across said input for initiating shunt current flow on the occurrence of a fault to divert current from said static circuit means, and second switching means intermediate said first switching means and said semiconductor for blocking current flow in each said main semiconductor to render the latter non-conductive on the occurrence of a fault, said protection means further including time delay means for blocking said shunt current following a first predetermined time after said shunt current is established whereby said DC voltage rises thereupon if said fault has ceased after said first predetermined time, said second switching means being responsive to said voltage sensing means to start conducting again when said fault has ceased after said first predetermined time.

Claim 23

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter stopping current in a conducting main semiconductor, said protection means comprising voltage sensing means responsive to produce a signal upon occurrence of a voltage across said input below a predetermined level, said protection means further comprising first switching means connected in shunt across said input for initiating shunt current flow on the occurrence of a fault to divert current from said static circuit means, and second switching means intermediate said first switching means and said semiconductor for blocking current flow in each said main semiconductor to render the latter non-conductive on the occurrence of a fault, said protection means further including time delay means for blocking said shunt current following a first predetermined time after said shunt current is established whereby said DC voltage rises thereupon if said fault has ceased after said first predetermined time, said second switching means being responsive to said voltage sensing means to start conducting again when said fault has ceased after said first predetermined time.

Claim 24

An electrical system for supplying power to an ac load from a dc electrical source comprising static inverter means having an input connected with said dc source and having output terminals connected for delivering ac power to the load, said static inverter means comprising a plurality of main Semiconductor means carrying load current and periodically rendered conductive and non-conductive at respective times to control the power to the load, sensing means for sensing the occurrence of a fault in said system and producing a signal thereupon, means for protecting said system comprising means responsive to said signal for diverting away from at least one main semiconductor means at least a portion of the current being conducted upon occurrence of the fault, time delay means responsive to the sensing of the fault by said sensing means for establishing a time delay following occurrence of the fault, means responsive to said time delay means for momentarily disabling said current-diverting means at the end of said time delay, control means for restoring normal operation upon said disabling in situations in which the fault has ceased during said delay and disconnect means controlled by an output from said sensing means for interrupting the supply of power for said inverter means in situations in which the fault has not ceased within a predetermined cumulative time but after said attempt to restore normal operation.

Claim 25

An electrical system for supplying power to an ac load from a dc electrical source comprising static inverter means having an input connected with said dc source and having output terminals connected for delivering ac power to the load, said static inverter means comprising a plurality of main Semiconductor means carrying load current and periodically rendered conductive and non-conductive at respective times to control the power to the load, sensing means for sensing the occurrence of a fault in said system and producing a signal thereupon, means for protecting said system comprising means responsive to said signal for diverting away from at least one main semiconductor means at least a portion of the current being conducted upon occurrence of the fault, time delay means responsive to the sensing of the fault by said sensing means for establishing a time delay following occurrence of the fault, means responsive to said time delay means for momentarily disabling said current-diverting means at the end of said time delay, control means for restoring normal operation upon said disabling in situations in which the fault has ceased during said delay and disconnect means controlled by an output from said sensing means for interrupting the supply of power for said inverter means in situations in which the fault has not ceased within a predetermined cumulative time but after said attempt to restore normal operation.

Claim 26

An electrical system as defined in claim 14 and wherein said means for diverting current comprises semiconductor means shunt-connected across said DC electrical source and seriesconnected semiconductor means intermediate said shunt connected semiconductor means and said plurality of main semiconductor means for disconnecting said input of said inverter from said DC source, and said means for momentarily disabling said current diverting means at the end of said time delay comprises commutating means for extinguishing conduction in said shunt-connected semiconductor means, and said control means for restoring normal operation upon said disabling comprises means for reconnecting said inverter input to said DC source.

Claim 27

An electrical inverter as defined in claim 13 in which said time delay means comprises a tank circuit including a capacitor in series with an inductor across said input and responsive to the shunt switching action of said first switching means upon a fault, and a rectifier connected across said input for recharging said capacitor and poled to block current from said source.

Claim 30

A method for protecting a static inverter as defined in claim 17 and wherein said step of establishing a substitute current path upon a fault comprises establishing a substitute current path in auxiliary commutation semiconductor means that perform routine commutation of said main SCRs during normal inverting operation of said inverter in the absence of a fault.

Claim 31

An electrical system for supplying power to an AC load from a DC electrical source comprising static inverter means having an input connected with said DC source and having output terminals connected for delivering AC power to the load, said static inverter means comprising a plurality of main semiconductor means carrying load current and each periodically rendered conductive and non-conductive to control the power to the load, a plurality of auxiliary commutation semiconductor means for routinely commutating off said main semiconductor means during inverting operation in the absence of a fault, sensing meanS for sensing the occurrence of a fault in said system and for producing a signal thereupon, means for protecting said system upon a fault comprising means responsive to said signal for rendering conductive at least momentarily at least one of the non-conducting ones of said auxiliary commutation semiconductor means to complete an additional current path to divert away from at least one of said main semiconductor means a portion of the current being conducted therethrough upon occurrence of the fault, and disconnect means controlled by an output from said sensing means for interrupting the supply of power for said inverter means after a predetermined time and after said diverting away of said portion of said current.

Claim 32

An electrical system for supplying power to an AC load from a DC electrical source comprising static inverter means having an input connected with said DC source and having output terminals connected for delivering AC power to the load, said static inverter means comprising a plurality of main semiconductor means carrying load current and each periodically rendered conductive and non-conductive to control the power to the load, a plurality of auxiliary commutation semiconductor means for routinely commutating off said main semiconductor means during inverting operation in the absence of a fault, sensing meanS for sensing the occurrence of a fault in said system and for producing a signal thereupon, means for protecting said system upon a fault comprising means responsive to said signal for rendering conductive at least momentarily at least one of the non-conducting ones of said auxiliary commutation semiconductor means to complete an additional current path to divert away from at least one of said main semiconductor means a portion of the current being conducted therethrough upon occurrence of the fault, and disconnect means controlled by an output from said sensing means for interrupting the supply of power for said inverter means after a predetermined time and after said diverting away of said portion of said current.

Claim 33

An electrical system as defined in claim 19 and wherein said means for protecting said system further comprises means responsive to said signal for rendering conductive at least momentarily in addition at least one of the non-conducting ones of said main semiconductor means to divert away from at least one conducting one of said main semiconductor means a portion of the current being conducted therethrough upon occurrence of said fault.

Claim 34

An electrical system according to claim 19 wherein said disconnect means is a contactor.

Claim 35

An electrical circuit as defined in claim 19 wherein each main semiconductor means comprises a gatable avalanche type of semiconductor device.

Claim 36

An electrical system as defined in claim 21 and wherein said contactor comprises time delay contactor means for interrupting said supply of power after said signal from said sensing means has existed for said predetermined time.

Claim 37

An electrical system as defined in claim 14 and wherein said means for diverting current comprises means for producing conduction in the previously non-conductive ones of said main semiconductor means, and said means for momentarily disabling said current-diverting means at the end of said time delay comprises commutating circuit means for extinguishing conduction in said main semiconductor means, and said control means for restoring normal operation comprises logic circuit means for triggering said main semiconductor means in a normal non-fault sequence.

Claim 38

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the re-establishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means.

Claim 39

An electrical system for transmitting power from an electrical DC source to a load comprising static circuit means having an input connected to said source and including at least one main load current semiconductor in which load current conduction is periodically started and extinguished for converting DC to AC, protection means for sensing a fault producing a current overload in said static circuit means and for diverting current from each conducting main semiconductor and for thereafter commutating off any conducting main semiconductor, said protection means comprising switching circuit means for momentarily establishing a shunt current across said input on the occurrence of a current overload to divert load current from said static circuit means and second switching means responsive to the establishment of said shunt current to block current conduction to said static circuit means and responsive to the re-establishment of source voltage across said static circuit means on the cessation of shunt current to re-establish load current to said static circuit means.

Claim 40

An electrical system for supplying power to an AC load of at least one phase from a DC electrical source comprising static inverter means having an input connected with said DC source and having output terminals connected for delivering AC power to the load, said static inverter means comprising a plurality of main semiconductor means carrying load current and each periodically routinely rendered conductive and non-conductive to control the power to the load, a plurality of commutation semiconductor means for rendering said main semiconductor means non-conductive, sensing means for sensing the occurrence of a fault in said system and producing a signal thereupon, disconnect meanS controlled by an output from said sensing means for interrupting the supply of power for said inverter means after a predetermined time, means for protecting said system comprising means for rendering conductive at least one of said commutation semiconductor means per phase so as to render non-conductive at least one of said main semiconductor means per phase when the phase has a conducting main semiconductor means, and means for restoring conductivity routinely to said main semiconductor means before said predetermined time, whereby said disconnect means does not interrupt said supply of power.

Claim 41

An electrical system for supplying power to an AC load of at least one phase from a DC electrical source comprising static inverter means having an input connected with said DC source and having output terminals connected for delivering AC power to the load, said static inverter means comprising a plurality of main semiconductor means carrying load current and each periodically routinely rendered conductive and non-conductive to control the power to the load, a plurality of commutation semiconductor means for rendering said main semiconductor means non-conductive, sensing means for sensing the occurrence of a fault in said system and producing a signal thereupon, disconnect meanS controlled by an output from said sensing means for interrupting the supply of power for said inverter means after a predetermined time, means for protecting said system comprising means for rendering conductive at least one of said commutation semiconductor means per phase so as to render non-conductive at least one of said main semiconductor means per phase when the phase has a conducting main semiconductor means, and means for restoring conductivity routinely to said main semiconductor means before said predetermined time, whereby said disconnect means does not interrupt said supply of power.